Stacey E. Iobst, Phd, RN [email protected]

Stacey E. Iobst, Phd, RN Siobst@Gmail.Com

Factors Influencing the Use of Labor Management Interventions and Their Effect on Cesarean Birth

Item Type dissertation

Authors Iobst, Stacey Elaine

Publication Date 2018

Abstract Background: The cesarean birth (CB) rate of 31.9% in the US is concerning because the procedure is associated with increased maternal mortality as well as increased maternal and neonatal morbidity. Women considered low-risk for CB are defined as null...

Keywords cervical dilation; intrapartum interventions; low-risk pregnancy; NTSV; Cesarean Section; Labor, Obstetric

Download date 30/09/2021 10:30:19

Link to Item http://hdl.handle.net/10713/7939 Stacey E. Iobst, PhD, RN [email protected]

EDUCATION Doctor of Philosophy 5/18 University of Maryland, Baltimore Baltimore, Maryland

Teaching Certificate, Nursing and Health Professions 12/17 University of Maryland School of Nursing Baltimore, Maryland

Bachelor of Science, Nursing, Magna Cum Laude 5/07 University of Maryland School of Nursing Rockville, Maryland

Bachelor of Arts, Biology 5/00 St. Mary’s College of Maryland St. Mary’s City, Maryland

LICENSURE Licensed Registered Nurse, Maryland Board of Nursing, R181555 Exp. 1/20

CERTIFICATIONS National Certification Corporation, ID104361835 Inpatient Obstetrics (RNC-OB) Exp. 6/19 Electronic Fetal Monitoring (C-EFM) Exp. 9/20 American Heart Association, Basic Life Support Exp. 2/19 American Academy of Pediatrics, Neonatal Resuscitation Exp. 7/18

WORK EXPERIENCE Clinical Nurse Holy Cross Hospital, Silver Spring, Maryland Labor and Delivery Unit 7/10 to date Women’s Surgical Unit 4/08-7/10

Clinical Nurse Georgetown University Hospital, Washington, D.C. Medical Intensive Care Unit 8/07-4/08

Guided Study Session Tutor University of Maryland School of Nursing, Rockville, Maryland Center for Academic Success 8/06-12/06

Research Associate III The Institute for Genomic Research (TIGR), Rockville, Maryland 1/01-12/05

HONORS AND AWARDS Research Institute Trainee Award-2017 Annual Meeting 10/16 Patient-Centered Outcomes Research Institute Washington, D.C.

Star of the Quarter 6/09 Holy Cross Hospital, Silver Spring, MD

Alumni Association Award for Leadership 5/07 University of Maryland School of Nursing, Baltimore, MD

ORGANIZATIONAL MEMBERSHIPS Graduate Nursing Student Academy (GNSA) Washington, D.C. Liaison to AACN Task Force-Defining Scholarship in Academic Nursing 2/17-8/17 Leadership Council Member 8/15-8/17

Doctoral Student Organization, University of Maryland School of Nursing Baltimore, Maryland PhD Curriculum Committee Representative 8/17 to date First Year PhD Program Representative 8/15-5/16

Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN) Member ID36761720 6/13 to date Maryland Section Social Media Editor 11/16 to date Montgomery County, Maryland Chapter Co-Coordinator 11/16 to date

Holy Cross Hospital Nursing Practice and Education Council Silver Spring, Maryland Co-Chair, Nursing Division 5/10-1/11 Secretary, Nursing Division 12/09-5/10 Chair, Women’s Surgical Unit 1/08-7/10

Sigma Theta Tau International Nursing Honor Society Pi Chapter Induction, Member ID 0521112 5/07

University of Maryland School of Nursing Student Government Association Universities of Shady Grove Campus, Rockville, Maryland Vice President 8/05-5/07

PRESENTATIONS Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN) Oral Presentation: “Shared Decision Making for Elective Induction of Labor” 10/17 Maryland Section Conference, Baltimore, Maryland

Poster: “Shared Decision Making for Induction of Labor” 6/17 National Conference, New Orleans, Louisiana

University of Maryland School of Nursing Baltimore, Maryland Three-Minute Thesis Competition (3MT) 11/16, 02/18

FUNDING Future of Nursing Scholar 8/15-5/18 Robert Wood Johnson Foundation at Johnson and Johnson, Inc., $75,000 University of Maryland School of Nursing, $50,000 matching funds

Doctoral Student Grant Award 7/17-6/18 Sigma Theta Tau International, Pi Chapter, $1,500

Donor Scholarships Frank and Robin Newhouse Scholarship, $1,035 10/17 Dean Janet D. Allan Scholarship, $1,000 11/17

PUBLICATIONS (*Indicates data-based) Published Manuscripts: *Iobst, S. (2017). Shared decision making for induction of labor. Journal of Obstetric, Gynecologic, and Neonatal Nursing, 46(3), S47.

*Jakubovics, N., Gill, S., Iobst, S., Vickerman, M., Kolenbrander, P. (2008). Regulation of gene expression in a mixed-genus community: stabilized arginine biosynthesis in Streptococcus gordonii by coaggregation with Actinomyces naeslundii. Journal of Bacteriology, 190(10), 3646-3657.

*Vickerman, M., Iobst, S., Jesionowski, A., Gill, S.R. (2007). Genome-Wide Transcriptional Changes in Streptococcus gordonii in Response to Competence Signaling Peptide. Journal of Bacteriology, 189(21), 7799-7807.

*Rensink, W., Iobst, S., Hart, A., Stegalkina, S., Liu, J., Buell, C. (2005). Gene expression profiling of potato responses to cold, heat, and salt stress. Functional Integrative Genomics, 5(4), 201-207.

*Rensink, W., Lee, Y., Liu, J., Iobst, S., Ouyang, S., Buell, C. (2005). Comparative analyses of six solanaceous transcriptomes reveal a high degree of sequence conservation and species-specific transcripts. BMC Genomics, 6(1),124.

*The International Rice Genome Sequencing Project. (2005). The map-based sequence of the rice genome. Nature, 436, 793-800.

*The Rice Chromosome 10 Sequencing Consortium. (2003). In-depth view of structure, activity, and evolution of rice chromosome 10. Science, 300(5625),1566-1569.

Abstract

Dissertation Title: Factors Influencing the Use of Labor Management Interventions and

Their Effect on Cesarean Birth

Stacey E. Iobst, Doctor of Philosophy, 2018

Dissertation Directed by:

Meg Johantgen, PhD, RN

Associate Professor

Associate Dean of the PhD Program

University of Maryland School of Nursing

Background: The cesarean birth (CB) rate of 31.9% in the US is concerning because the procedure is associated with increased maternal mortality as well as increased maternal and neonatal morbidity. Women considered low-risk for CB are defined as nulliparous and pregnant with a term, singleton gestation in the vertex position (NTSV). Even among

NTSV women, cesarean rates range from 2.4% to 36.5% across hospitals, suggesting that

CB may be influenced by differences in practice patterns, including admission triage, the use of labor management interventions (e.g., amniotomy, epidural analgesia, and oxytocin augmentation), and availability of a laborist.

Purpose: The following were examined in three manuscripts: (1) influence of cervical dilation at admission on labor management and CB, (2) influence of provider and hospital characteristics on labor management and CB, (3) influence of combinations of labor management interventions on likelihood of CB.

Methods: All three manuscripts were cross-sectional, observational studies of NTSV women with spontaneous onset of labor whose births occurred from 2002-2007 at

hospitals included in the National Institutes of Health Consortium on Safe Labor.

Samples sizes varied due to missing data but ranged from 17,443 to 26,259. Generalized linear mixed modeling was used to account for the effects of hospital and provider clusters.

Results: Greater dilation at admission (>6 cm) was associated with a lower likelihood of receiving all three interventions (RR 0.40, CI95 0.35-0.46) and a lower likelihood of CB

(4-5 cm: RR 0.44, CI95 0.40-0.49; >6 cm: RR 0.20, CI95 0.17-0.24). Midwives were more likely to use no interventions compared to obstetrician/gynecologists (RR 1.81,

CI95 1.50-2.19). Women delivering at hospitals with an as-needed laborist available had a greater likelihood of receiving no interventions (RR 4.27, CI95 1.43-12.70) compared to those at hospitals with a 24/7 laborist. Compared to no interventions, use of all three interventions was associated with an increased likelihood of CB (RR 1.84, CI95 1.53-

2.21).

Conclusion: Admitting women at more advanced cervical dilation may reduce the use of labor management interventions and CB. The combined use of labor management interventions should be considered carefully given the association with an increased likelihood of CB.

Factors Influencing the Use of Labor Management Interventions and Their Effect on Cesarean Birth

by Stacey E. Iobst

Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, Baltimore in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2018

This dissertation is dedicated to the many inspirational women who have motivated me to persist in fighting the good fight.

iii

Acknowledgements

I would like to acknowledge the Robert Wood Johnson Foundation (RWJF) and Johnson and Johnson, Inc., for providing the support necessary to complete my PhD in three years. I was committed to the RWJF Future of Nursing Program the moment I learned of their goal to increase the number of PhD-prepared nurses in order to bring transformational change to healthcare in the United States. I am grateful especially to Dr. Sue Hassmiller, Dr. Julie Fairman, and Heather Kelley-Thompson, for their unwavering support and mentorship throughout my PhD program.

I am grateful to the members of my dissertation committee for supporting me along this journey. Many thanks to my dissertation chair, Dr. Meg Johantgen, for obtaining support from the RWJF and for spending countless hours working with me to develop and defend my dissertation. Dr. Johantgen, I strive to someday be an educator and researcher of your caliber. Your patience and dedication are unmatched. I am grateful to Dr. Carla Storr for keeping me grounded in the scientific process while also being a constant source of positive energy and support. Thanks to Dr. Shijun Zhu for providing statistical expertise, often via lengthy e-mail exchanges at odd hours and often with greater frequency preceding looming deadlines. I am grateful to Dr. Eleanor Perfetto for providing me with a broader perspective on healthcare policy, patient-centered research, and quality measurement. Thanks also to Dr. Debra Bingham for her expertise and guidance based on over thirty years of work in maternity care.

I would also like to thank two of my best friends and fellow PhD students, Alisha Hackney and Rachel Breman. I began the PhD program with Ali, and as my fellow RWJF Future of Nursing Scholar at the University of Maryland, we have supported each other through our fast track PhD programs. Ali, thank you for setting an example through your intellectual curiosity and strong work ethic. Thank you also for always listening with a compassionate heart and for reminding me of the important things in life. I will always believe that fate brought me and Rachel together. At a research meeting early in our programs we realized that we were kindred spirits, both living in Silver Spring, Maryland, with children at the same preschool, and having a shared passion for maternity care research. Rachel, thank you for always believing in me and for showing me that all things are possible. Your grit and determination are an inspiration.

I would like to thank my family for providing unconditional love and support from the very beginning of this journey. I am grateful to my mother, Susan Rabern, for showing me the value of hard work and integrity. Mom, you are the fiercest, yet humblest dragon lady I’ve ever known. Thank you to my father, Jim Blunt, for teaching me to take time for family and fun. Dad, I am so grateful for our routine visits and “radio checks”, both of which have preserved my sanity and kept me focused on the true priorities in life. My children, Jesse and Julie, have shown me tremendous love and support throughout this process. I am grateful for their patience and encouraging hugs along the way. And finally, words cannot express my appreciation for my husband, Adam Iobst. Adam, you’ve always known exactly what I need when I need it. I am certain that I would not have accomplished this great achievement without your steadfast love and support.

Table of Contents

Chapter 1: Introduction and Purpose ...... 1 1.1 Introduction ...... 1 1.2 Literature review ...... 3 1.3 Purpose and Specific Aims ...... 9 1.4 Conceptual Framework ...... 10 1.5 Methods...... 11 1.6 Ethical Considerations ...... 13 1.7 Organization of the Study ...... 13 Chapter 2: Influence of Admission Dilation on Intrapartum Interventions and Cesarean Birth on Low-Risk Women ...... 14 2.1 Abstract ...... 14 2.2 Background ...... 15 2.3 Methods...... 17 2.4 Results ...... 20 2.5 Discussion ...... 24 Chapter 3: Influence of Hospital and Provider Characteristics on Intrapartum Interventions and Cesarean Birth in NTSV Women ...... 29 3.1 Abstract ...... 29 3.2 Introduction ...... 30 3.3 Methods...... 32 3.4 Results ...... 35 3.5 Discussion ...... 43 Chapter 4: Influence of Amniotomy, Epidural Anesthesia, and Oxytocin Augmentation on Cesarean Birth in Low-Risk Pregnancies ...... 48 4.1 Abstract ...... 48 4.2 Introduction ...... 49 4.3 Methods...... 50 4.4 Results ...... 53 4.5 Discussion ...... 56 Chapter 5: Discussion ...... 62 5.1 Summary of Findings ...... 62 5.2 Strengths, Limitations, and Recommendations ...... 65 5.3 Policy and Practice Implications ...... 70 5.4 Conclusion ...... 72 References ...... 73

List of Tables

Table 2.1. Characteristics of sample by cervical dilation at admission (n=21858) ...... 21

Table 2.2. Interventions and delivery mode by dilation at admission...... 22

Table 2.3. Relative risk of interventions and cesarean birth by dilation at admission ..... 24

Table 3.1. Provider and maternal characteristics ...... 36

Table 3.2. T-tests comparing physician-level cesarean birth rates by physician characteristics ...... 39

Table 3.3. Relative risk of intrapartum interventions by provider characteristics ...... 42

Table 4.1. Demographic characteristics by delivery mode (n=26,259) ...... 54

Table 4.2. Relative risk of cesarean birth by intrapartum interventions ...... 56

List of Figures

Figure 1.1. Coyle and Battles version of the Donabedian Model ...... 10

Figure 1.2. Sample selection for each aim ...... 13

Figure 2.1. Sample selection (n=21,858) ...... 18

Figure 2.2. Percentage of sample receiving number of interventions by dilation at admission ...... 22

Figure 3.1. Sample selection (n=17,443) ...... 33

Figure 3.2. T-tests comparing physician-level cesarean birth rates by physician characteristics ...... 38

Figure 4.1. Sample selection (n=26,259) ...... 52

Figure 4.2. Intrapartum interventions by delivery mode ...... 55

vii

Abbreviations

Abbreviation Terms

ACOG American College of Obstetricians and Gynecologists

BMI Body Mass Index

CB Cesarean Birth

CSL Consortium on Safe Labor

ICC Intra-class Correlation

MFM Maternal Fetal Medicine

NICU Neonatal Intensive Care Unit

NTSV Nulliparous, Term, Singleton, Vertex

OB/GYN Obstetrician/Gynecologist

SMFM Society for Maternal Fetal Medicine

viii

Chapter 1: Introduction and Purpose

1.1 INTRODUCTION

The cesarean birth rate in the United States has risen dramatically in recent history from 5.5% in 19701 to the current rate of 31.9%.2 Although lifesaving in certain circumstances, overuse of cesarean birth is a public health concern because the procedure is associated with increased mortality and morbidity. Most notably, cesarean birth is associated with a nearly four times greater rate of maternal mortality in comparison with vaginal birth.3 Women who undergo cesarean birth also have increased morbidity including greater risk of infection, venous thromboembolism, postpartum hemorrhage, hysterectomy, and placental complications in future pregnancies.4–7 For neonates, cesarean birth is associated with increased risk of respiratory morbidity and admission to the neonatal intensive care unit (NICU) as well as asthma, obesity, and type I diabetes mellitus in childhood.8–12

Although the national cesarean birth rate has stabilized in recent years, the current rate of 31.9% likely represents overuse of the procedure based on evidence that cesarean birth rates above 10%-19% are not associated with reductions in maternal and neonatal mortality.13,14 Another trend that suggests overuse of cesarean birth is the wide variation of rates, ranging from 22.8% to 38.2% across states15 and from 7.1% to 69.9% across hospitals.16 Cesarean birth rates vary even more widely among women who are low risk for the procedure, defined as nulliparous and pregnant with a term, singleton gestation in the vertex position (NTSV). Among NTSV pregnancies, cesarean birth rates vary from

2.4 to 36.5% across hospitals.16 These statistics for low-risk women are particularly concerning because 90% of women who undergo cesarean birth will deliver by the same

1 route in subsequent pregnancies.17 Moreover, repeated cesarean birth is associated with increased maternal morbidity over and above the first cesarean, including blood transfusion, hysterectomy, and surgical injury.18,19 Therefore, prevention of the first cesarean birth is a key strategy to reduce the overall rate as well as to avoid the cumulative increase in maternal morbidity associated with repeated cesarean deliveries.

Several factors are independently associated with cesarean birth including older maternal age, maternal obesity, and African American ethnicity.20–24 However, the rise in cesarean birth has been observed across all maternal ages, races, gestational ages, and states regardless of changes in maternal risk profiles.22,25 A possible etiology of the increase in cesarean birth is the variation in practice among healthcare systems, hospitals, and providers.3 In particular, certain practice patterns may result in a phenomenon referred to as the “cascade effect” whereby the sequential application of labor management interventions ultimately results in cesarean birth.26,27 The cascade begins upon admission because hospital policy often dictates the initiation of continuous intravenous fluid infusion and electronic fetal monitoring upon admission.28 These interventions restrict maternal mobility, limiting the ability to use non-pharmacologic pain management techniques. Epidural anesthesia may then be applied to manage pain associated with uterine contractions. In addition to further limiting mobility, epidural anesthesia has also been shown to interfere with the release of oxytocin, resulting in slowed labor progression.29 Thus, interventions such as amniotomy and oxytocin may be applied to augment labor. This cascade effect is concerning because the increased application of interventions is positively associated with cesarean birth.30,31 Additionally, evidence showing an association between admission in early labor and cesarean birth

2 suggests that earlier admission may lead to increased use of labor management interventions.32–36

According to a nationally representative survey of postpartum women, the majority reported receiving multiple labor management interventions such as those occurring as part of the cascade effect.37 Existing literature is focused on the use of single interventions or pairs of interventions rather than the cumulative effect of interventions applied in combination. Therefore, the current evidence may not fully represent the clinical experience of most women in the United States. The following review of the literature demonstrates that a gap remains regarding the influence of maternal, provider, and hospital characteristics on patterns of labor management interventions. Moreover, no research was found that has examined the cumulative effect of labor management interventions used in combination (amniotomy, epidural, oxytocin augmentation) on the likelihood of cesarean birth.

1.2 LITERATURE REVIEW

Influence of Non-Clinical Factors on Cesarean Birth

Maternal Characteristics. Most research examining the relationship between maternal characteristics and cesarean birth has focused on maternal demographics. A meta-analysis of 11 cohort studies found that the pooled odds of having an emergency cesarean birth were 1.64 (CI95 1.55-1.73) for overweight women and 2.23 (CI95 2.07-

2.42) for obese women.20 Older maternal age has also been found to be positively associated with cesarean birth. A systematic review found that all 21 studies included in the review showed increased risk of cesarean birth among women at advanced maternal age (>35 years) compared to younger women, regardless of parity (RR 1.39-2.76).21

According to national statistics from the CDC, Non-Hispanic Black women also had a higher rate of cesarean birth (35.9%) in comparison with Non-Hispanic White women

(30.9%) in 2016.38 A study of n=540,953 deliveries in Kaiser Permanente Southern

California found that Black women had a consistently higher rate of primary cesarean birth compared to all other races from 1991-2008.23 During this timeframe, Black women had a 25% higher likelihood of primary cesarean birth (CI95 16-23%) compared to White women.

Several studies conducted both in the United States and elsewhere have examined the relationship between cervical dilation at admission and the outcome of cesarean birth in nulliparous women. The results across studies were consistent, showing that admission at lower cervical dilation is associated with a 1.5 to 2.6 times higher likelihood of cesarean birth.32–36 Early labor was defined differently in each study, ranging from less than 1.5 cm to less than 5 cm of cervical dilation. One study differentiated participants according to whether they were in pre-active labor, defined as average dilation less than

0.5 cm/hour during the first 4 hours after admission.33 Another study defined the active phase of labor as the presence of regular, painful contractions with cervical dilation greater than 3 cm.35 It is noteworthy that in 2010 an examination of labor progression in contemporary women resulted in a revised benchmark for active labor of 6 cm of cervical dilation.3,39

Hospital Characteristics. The influence of hospital characteristics on cesarean birth has been examined to a fair extent in the Unites States and Canada. In particular, obstetric model of care, type of hospital, and level of NICU have been investigated in relation to cesarean birth. One study conducted in California compared a traditional

4 private practice model against a laborist model.40 In the private practice model, physician providers may be on call from home or while working in outpatient offices whereas in the laborist model there were midwives or physicians available at the hospital at all times.

Results showed a higher rate of NTSV cesarean birth (29.8%) in the private practice model compared to the laborist model (15.9%). A similar study conducted in Las Vegas,

Nevada, compared three clinical models: care provided through a traditional private practice model (no laborist), contracted care provided 24/7 by local community physicians (community laborist), and a 24/7 dedicated full-time laborist staff.41 Results showed that having a full-time laborist was associated with a lower likelihood of cesarean birth compared with having no laborist (OR 0.73, CI95 0.64-0.83) or having community laborists (OR 0.77, CI95 0.67-0.87). A Canadian study comparing cesarean birth rates at a tertiary hospital versus a community hospital found that the tertiary hospital had a greater likelihood of cesarean birth in nulliparous pregnancies with a term, singleton gestation (OR 3.4, CI95 2.1-5.4).42 Results from two studies conducted in the United

States found mixed results regarding the relationship between level of NICU and cesarean birth for nulliparous women.24,43

Provider Characteristics. The few provider characteristics that have been examined with respect to influence on cesarean birth include provider type (physician versus midwife), provider sex, and practice type. A Cochrane systematic review comparing midwifery-led care with other models of care found a lower likelihood of cesarean birth associated with midwifery-led care (RR 0.92, CI95 0.84-1.00).44 Two studies conducted in the United States found that male providers as well as providers who are university faculty have a higher likelihood of performing cesarean birth.43,45

Influence of Non-Clinical Factors on Labor Management Interventions

Maternal Characteristic: Cervical Dilation at Admission. Two studies have examined the influence of cervical dilation at admission on the use of labor management interventions. In one study conducted in the Midwestern United States, NTSV women admitted in pre-active labor were more likely to receive oxytocin augmentation (OR 6.5,

CI95 3.43-12.27) but less likely to receive amniotomy (OR, 0.8; CI95, 0.44–1.32) compared to women admitted in active labor.33 A study of 14 hospitals in Washington

State found that nulliparous women admitted prior to 4 cm cervical dilation had an increased likelihood of epidural (RR 1.18, CI95 1.13-1.24) and oxytocin augmentation

(RR 1.56, CI95 1.50-1.63).36

Provider characteristics. Two systematic reviews were identified that examined care provided by midwives. One review found that care provided by certified nurse midwives was associated with lower use of epidural, labor induction, and episiotomy.46 A

Cochrane systematic review comparing midwifery-led care to other models of care included 15 high-quality studies that were conducted in Australia, Canada, Ireland and the United Kingdom. Results showed that midwifery-led care was associated with a lower likelihood of epidural/spinal anesthesia (RR 0.85, CI95 0.78-0.92), amniotomy

(RR 0.80, CI95 0.66-0.98), and oxytocin augmentation (RR 0.88, CI95 0.78-0.99).40

Influence of Labor Management Interventions on Cesarean Birth

Several Cochrane systematic reviews have explored the relationship between labor management interventions and cesarean birth, but results vary depending on whether the review examined a single intervention or a pair of interventions. For instance, amniotomy alone was found to increase the risk of cesarean birth (RR 1.15,

CI95 0.88-1.51),48 but early amniotomy combined with early oxytocin reduced the risk of cesarean birth (RR 0.89, CI95 0.79, 1.01).49 Similarly, the use of epidural alone showed a slight increase in the risk of cesarean birth (RR 1.10, CI95 0.97-1.25),50 but oxytocin augmentation in women also receiving epidural anesthesia showed a decreased risk of cesarean birth (RR 0.95, CI95 0.42-2.12).51

One systematic review attempted to model the cascade effect by examining relationships between pairs of labor management interventions (electronic fetal monitoring, epidural, labor induction, and labor augmentation) and type of delivery

(instrumental vaginal birth and cesarean birth) in low-risk women.27 Results showed that epidural was associated with higher odds of cesarean birth (OR 1.60, CI95 1.18–2.18) and use of oxytocin (OR 1.20, CI95 1.01–1.43) when compared with epidural plus non- pharmacological methods of pain control. Findings were mixed for the relationship between labor augmentation and type of birth (cesarean or operative vaginal birth).

Although the systematic review included only studies that examined low-risk women, the meta-analyses included both nulliparous and multiparous women. Therefore, results from this systematic review cannot be generalized specifically to nulliparous women having their first birth.

Two primary studies have examined the use of amniotomy, epidural, and oxytocin. One study conducted in Australia examined the association between labor management interventions and unassisted vaginal birth among low-risk women from

2000-2002.31 Results showed that low-risk NTSV women who underwent labor induction or augmentation were twice as likely (AOR 2.04, CI99 1.79-2.32) to have a cesarean birth. Women who received epidural and labor induction or augmentation had a 52.18

7 times greater odds of cesarean birth (AOR 52.18, CI99 46.92-58.04). Generalizability of these results to the population in the United States is limited due to differing incentives in the universal healthcare system in Australia. A second limitation was that induction and augmentation of labor were grouped together as one category. This is problematic because women undergoing induction of labor require interventions to initiate and sustain labor. Therefore, the use of multiple interventions is likely to be greater in women who are induced compared to those with spontaneous onset of labor.

The second primary study to examine the use of amniotomy, epidural anesthesia, and oxytocin augmentation was conducted in Germany in 2005. The aims of the three publications resulting from the parent study were the following: (1) to describe the timing of labor interventions52, (2) to model the sequence and timing of interventions and examine association with length of labor and delivery mode,53 and (3) to examine the association of various timings of labor interventions with duration of labor and delivery mode.54 Findings relevant to this dissertation showed that as the number of interventions increased, the number of spontaneous vaginal births decreased.53 Additionally, results for nulliparous women showed that oxytocin augmentation was associated with a greater likelihood of cesarean birth (HR=2.2 CI95 1.65-2.97).54 One limitation of this study is that motivations and payment systems are likely to influence practice patterns differently in Germany than in the private payer system in the Unites States. A second limitation is that midwives were acknowledged as the main care provider during labor. This model is unlike the maternity care model in the United States where midwives attended only approximately 10% of births in 2015.55

1.3 PURPOSE AND SPECIFIC AIMS

The purpose of this dissertation was to examine factors that influence labor management interventions and their effect on cesarean birth in low-risk NTSV women with spontaneous onset of labor. This was accomplished through the following aims:

Aim 1: Determine if cervical dilation at admission (e.g., 3-4 cm, 4-5 cm, 6-10 cm) predicts the number and pattern of labor management interventions (e.g., amniotomy, epidural anesthesia, oxytocin augmentation) used individually and in combination as well as cesarean birth for NTSV women with spontaneous onset of labor.

Hypothesis: NTSV women admitted in spontaneous labor at greater than 4 cm cervical dilation are less likely to receive a greater number of interventions, receive a combination of all three interventions, and have a cesarean birth.

Aim 2: Determine if provider characteristics (e.g., sex, practice type, specialty) and hospital characteristics (e.g., hospital type, obstetrics level, NICU level, availability of a laborist, availability of select obstetric and neonatal providers) predict patterns of labor management interventions (used individually and in combination) and cesarean birth for NTSV women with spontaneous onset of labor. Hypothesis: A physician provider and availability of a 24/7 laborist will independently predict the likelihood of interventions used individually and in combination as well as cesarean birth for NTSV women with spontaneous onset of labor.

Aim 3: Determine if patterns of labor management interventions used individually and in combination predict cesarean birth for NTSV women with spontaneous onset of labor. Hypothesis: NTSV women with spontaneous onset of labor who receive more interventions will have a greater likelihood of cesarean birth.

1.4 CONCEPTUAL FRAMEWORK

The Donabedian model provides a framework to examine the structure, process, and outcomes of healthcare56–58 (Figure 1.1). Structure refers to the context of care such as the physical environment, organizational characteristics, and qualifications of healthcare providers. Process includes the treatments or services provided to the patient.

Outcome refers to the consequences of care and is often used to measure quality of care.

Outcome typically refer to long-term consequences such as morbidity and mortality; however, in this dissertation outcome refers to a short-term intermediate consequence of care. The Coyle and Battles version of the Donabedian model also includes antecedents as a fourth concept in the framework to encompass patient characteristics and environmental risk factors.57 The Coyle and Battles version of the Donabedian model was used as a conceptual framework for this study where each concept was defined as the following: antecedents included cervical dilation at admission, structure included

provider and hospital characteristics, process included labor management interventions

Figure 1.1. Coyle and Battles version of the Donabedian Model (e.g., amniotomy, epidural anesthesia, and oxytocin augmentation), and outcome was cesarean birth.

1.5 METHODS

Data for this dissertation were obtained from the Consortium on Safe Labor

(CSL). The CSL was a multisite retrospective cohort study conducted by the Eunice

Kennedy Shriver National Institute of Child Health and Human Development of the

National Institutes of Health. The CSL collected data from n=228,438 deliveries that occurred in the United States from 2002-2008 with the majority of births taking place from 2005-2007. Deliveries occurred across 12 clinical sites that included 19 hospitals and represented nine districts of the American College of Obstetricians and

Gynecologists. There were 8 university-affiliated hospitals, 9 community teaching hospitals, and 2 community non-teaching hospitals. Selected clinical information was downloaded from hospital databases in de-identified format and some records were selected randomly for manual data abstraction. Provider and hospital characteristics were collected through administration of a technical survey at each clinical site. Data were downloaded to the CSL Data Coordinating Center where records were cleaned, coded, and audited. Quality assurance was conducted through random auditing of critical variables to confirm that the electronic medical records accurately reflected the medical charts. Additionally, electronically retrieved data were compared against manually abstracted data. Main components of the dataset include: maternal demographics, reproductive history, medical history, prenatal history of current pregnancy, labor admission assessment, labor progression, labor and delivery summary, maternal postpartum condition, and newborn information.

For this dissertation, a retrospective, observational study was conducted using a subset of participants from the CSL for each aim. Specific exclusion criteria were applied

11 to the CSL dataset to achieve a sample consisting of NTSV women with spontaneous onset of labor. The following exclusion criteria were applied: admission for spontaneous rupture of membranes without onset of labor, induction of labor, or pre-labor cesarean birth, (2) multiparous women, (3) preterm gestation (< 37 weeks), post-term gestation

(>42 weeks), or stillbirths, (4) multiple gestations, and (5) non-vertex presentation

(Figure 1.2). Each aim consisted of a different set of hospitals due to completely missing data or large amounts of missing data for main variables of interest. The resulting analytic files included the following for each aim: (Aim 1) 9 hospitals and n=21,858 deliveries, (Aim 2) 8 hospitals and n=17,443 deliveries, (Aim 3) 11 hospitals and 26,259 deliveries.

Detailed methods for each aim are described in chapters 2-4. In summary, intra- class correlations were calculated for relationships of interest and it was determined that hierarchical modeling was required to account for provider- and hospital-level effects.

Descriptive statistics were used to examine the samples, the use of labor management interventions both individually and in combination, and the use of cesarean birth.

Generalized linear mixed modeling was conducted to examine relationships of interest for each aim.

Figure 1.2. Sample selection for each aim

1.6 ETHICAL CONSIDERATIONS

Data were obtained from the Consortium on Safe Labor after signing a data use agreement. A review by the University of Maryland School of Nursing determined that the study was non-human subjects because the data were de-identified (FWA

#00007145).

1.7 ORGANIZATION OF THE STUDY

Chapters two, three, and four comprise three manuscripts that are consistent with the aims of this dissertation. Each manuscript was prepared for submission to peer- reviewed scientific journals in fulfillment of the manuscript option for dissertation.

Chapter five is a summary of the main findings in each manuscript as well as a discussion of limitations, implications of findings, and recommendations for future research.

Chapter 2: Influence of Admission Dilation on Intrapartum Interventions and

Cesarean Birth in Low-Risk Women

2.1 ABSTRACT

Background: Evidence has shown that admission in early labor is associated with increased likelihood of cesarean birth. However, the mechanism by which admission in early labor leads to cesarean is unclear. One possibility is that early admission leads to the increased use of intrapartum interventions and that cesarean birth results from the cumulative effect of interventions.

Objectives: The purpose of this study was to examine whether cervical dilation at admission influences: (1) amniotomy, epidural anesthesia, and oxytocin augmentation, used individually and in combination; and (2) cesarean birth.

Methods: This was a cross-sectional, observational study of 21,858 nulliparous singleton term vertex births that occurred from 2002-2007 across nine hospitals in the Consortium on Safe Labor.

Results: Most women (92%) received at least one intrapartum intervention and 22.7% received all three interventions. As cervical dilation at admission increased, the percentage of women receiving interventions decreased, regardless of whether women received one intervention (11.4% at 0-3 cm, 8.4% at 4-5 cm, and 5.8% at 6-10 cm), two interventions (24.6% at 0-3 cm, 13.5% at 4-5 cm, and 5.4% at 6-10 cm), or three interventions (14.0% at 0-3 cm, 7.4% at 4-5 cm, and 1.6% at 6-10 cm). Women were

55% less likely to receive the combination of amniotomy, epidural, and oxytocin when admitted at 6-10 cm (RR 0.40, CI95 0.35-0.46) compared to those admitted at 0-3 cm.

Likelihood of cesarean birth was lower for women admitted at 4-5 cm (RR 0.44, CI95

0.40-0.49) and 6-10 cm dilation (RR 0.20, CI95 0.17-0.24) compared to those admitted at

0-3 cm dilation.

Conclusions: Regardless of the total number of interventions applied, women receive fewer interventions as cervical dilation at admission increases beyond 3 cm. Admission at after 4 cm dilation is associated with a lower likelihood of cesarean birth, however it is unclear whether this is due to the use of intrapartum interventions.

Keywords: admission, cervical dilation, intrapartum interventions, cesarean birth

2.2 BACKGROUND

The rise in cesarean birth from 22.9% in 200059 to a current rate of 31.9%2 is a public health concern because the procedure is associated with increased maternal mortality as well as increased maternal and neonatal morbidity3. For women, adverse outcomes include postpartum hemorrhage, hysterectomy, and placental complications in future pregnancies.6,60–62 Neonates delivered by cesarean are at higher risk for increased respiratory morbidity and admission to the neonatal intensive care unit.8–10 While the national cesarean rate has been stable in recent years, worldwide ecological studies show that the optimal rate is between 15-19%.13,14,63 In the United States, current efforts are focused on preventing the first cesarean in women who are considered low-risk for the procedure, defined as nulliparous and pregnant with a single baby at term gestation in the vertex position (NTSV).

A key strategy to prevent the first cesarean birth is to delay admission to the hospital until the onset of active labor. Traditionally, onset of active labor has been defined as 3 cm to 5 cm of cervical dilation,64 but an examination of labor progression in contemporary women found that active labor begins at 6 cm or later.39 Some evidence

15 shows that admission prior to onset of active labor is associated with greater risk of cesarean birth.32–35 In particular, admission may initiate a cascade effect where the application of interventions such as continuous intravenous fluid infusion, continuous electronic fetal monitoring, and epidural anesthesia may limit mobility. Epidural anesthesia may also slow labor progression by interfering with the release of oxytocin.65

In some cases, this slowed progress may lead to the use of amniotomy or oxytocin to augment labor. Thus, the link between admission in early labor and cesarean birth may be explained by increased application of intrapartum interventions in response to slower labor prior to 6 cm of dilation. Evidence has shown that admission in early labor is associated with epidural anesthesia and amniotomy,33,36,66 but no literature was identified that has examined cervical dilation at admission in relation to the combined use of intrapartum interventions. Research is needed to explore whether admission in early labor is associated with increased use of interventions because some evidence shows that the sequential application of labor management interventions is associated with increased risk of cesarean birth.30,67

While examining interventions as isolated outcomes provides some information about intrapartum provider practices, this method does not account for the practice of applying multiple interventions over the course of labor. According to a nationally representative survey of postpartum women, the majority reported receiving multiple intrapartum interventions including continuous electronic fetal monitoring (89%), epidural anesthesia (62%), and oxytocin (50%).68 Therefore, analyzing interventions used in combination rather than in isolation is critical to understanding how intrapartum care occurs in the real world. Moreover, understanding how timing of admission influences

16 the use of intrapartum interventions may provide insight about how to prevent unnecessary cesarean birth in low-risk women. The purpose of this cross-sectional, observational study is to examine in NTSV women with spontaneous onset of labor the relationship between cervical dilation at admission and (1) the individual and combined use of amniotomy, epidural anesthesia, oxytocin augmentation, and (2) cesarean birth. It is hypothesized that admission at lower cervical dilation is positively associated with the use of more interventions and a higher likelihood of cesarean birth.

2.3 METHODS

The sample was a subset of participants from a multicenter retrospective observational study conducted by the National Institute of Child Health and Human

Development (NICHD), National Institutes of Health Consortium on Safe Labor. Data were collected between 2002-2008 from electronic medical records for 228,438 deliveries across 19 hospitals, including nine community teaching hospitals, eight university-affiliated teaching hospitals, and two non-teaching community hospitals. The majority of deliveries in the dataset (85%) occurred from 2005-2007. Hospital- and provider-level data were collected through a survey administered at each site. Data were obtained after completion of a data use agreement with the NICHD. The study was determined by the University of Maryland School of Nursing Institutional Review Board to be non-human subjects research due to the de-identification of data.

To produce the analytic data file, the following inclusion criteria were used: admission in spontaneous labor, nulliparous births, term births (gestational age 37 to 42 weeks of gestation), singleton births, and vertex presentations (Figure 2.1). Some hospitals from the Consortium on Safe Labor were excluded from this study due to

17 completely missing data or a large percentage of missing data for a main variable of interest. Nine hospitals had completely missing data for one or more of the following variables: amniotomy, epidural anesthesia, oxytocin augmentation, and dilation at admission. One hospital was excluded for 72% missing data for dilation at admission.

The resulting analytic file included births from n=21,858 women attended by 665 providers across nine hospitals from 2002-2007.

Outcomes of interest were the use of intrapartum interventions (amniotomy,

Figure 2.1. Sample selection (n=21,858) epidural anesthesia, oxytocin augmentation) and cesarean birth. Due to possible

18 clustering effects at the hospital and provider levels, intra-class correlations were calculated for each outcome. Based on intra-class correlations for hospital-level effects

(amniotomy=0.05, epidural=0.19, oxytocin=0.16, cesarean=0.02) and provider-level effects (amniotomy=0.02, epidural=0.20, oxytocin=0.17, cesarean=0.17), a multilevel approach was used. Intra-class correlation results were used to calculate design effects for each outcome for hospital-level clusters (amniotomy=0.95, epidural=6.87, oxytocin=5.92, cesarean=1.65) and provider-level clusters (amniotomy=1.55, epidural=7.40, oxytocin=6.45, cesarean=6.39). Required sample size was calculated a priori based on published effect sizes ranging from OR=0.8 to OR=6.5 for the relationship between cervical dilation at admission and the outcomes of amniotomy, epidural, oxytocin, and cesarean birth.33,34,36,66,69 Maximum required sample size was estimated at n=1,967 to detect an effect at 80% power with alpha level (two-sided)=0.05.

Therefore, the sample size of n=21,858 was determined to be more than adequate.

Descriptive statistics were used to examine sample characteristics, combination of interventions, and number of interventions by cervical dilation at admission. One-way

ANOVA and chi-squared were conducted to examine maternal characteristics by dilation at admission. Generalized linear mixed modeling was used to examine the relationship between cervical dilation at admission and: (1) intrapartum interventions used individually and in combination, and (2) cesarean birth. A small proportion of the sample had pregnancy risk factors such as gestational diabetes (2.3%), chronic hypertension

(0.3%), diabetes (0.5%), and preeclampsia (3.6%). Therefore, a variable was created to represent aggregated comorbidity for women having any of these risk factors. Bivariate analyses were used to examine maternal characteristics for inclusion in adjusted models.

These included age, body mass index (BMI), race, marital status, education level, insurance type, birth attendant, and comorbidity. Maternal age, BMI, and comorbidity were included in adjusted models based on bivariate results as well as evidence in the literature showing that maternal age and body mass index (BMI) are associated with cesarean birth.21,22,70 Data analyses were conducted using SAS version 9.4.

2.4 RESULTS

The sample included births of n=21,858 women occurring from 2002-2007 across nine hospitals. Table 2.1 describes the sample characteristics by three stages of cervical dilation at admission: 0-3 cm, 4-5 cm, and 6-10 cm. Mean age was 24.9 (±5.4) years and did not vary across dilation at admission: F (2, 21316) = 1.45, p=0.235. Mean BMI was

29.2 (±5.1) and there was strong evidence that BMI varied across dilation at admission when comparing each dilation group, but the effect was small: F (2, 16682) = 61.13, p<0.001, d=0.007. The majority was White/Non-Hispanic (71.0%), and married (68.4%).

Most women had greater than a high school education (60.2%) and most had private health insurance (78.9%). Physicians attended 88.3% of the deliveries. Results of chi- squared analyses showed strong evidence that sample characteristics differed by dilation at admission, possibly due to the large sample size.

Table 2.2 shows the use of intrapartum interventions and cesarean delivery by dilation at admission. About half of women were admitted at 0-3 cm of cervical dilation

(51.2%). Amniotomy-epidural-oxytocin was the most frequently used combination of interventions (22.7%) followed by amniotomy-epidural (21.4%) and epidural-oxytocin

(20.3%). Use of amniotomy-epidural-oxytocin and epidural-oxytocin decreased as cervical dilation at admission increased. In contrast, use of no interventions and single

20 interventions increased as cervical dilation at admission increased. The overall cesarean birth rate was 13.8%, and the rate for each group decreased with increasing cervical dilation at admission.

Table 2.1. Characteristics of sample by cervical dilation at admission (n=21858) Overall 0-3 cm 4-5 cm 6-10 cm (n=21858) (n=10943) (n=6759) (n=3659) Mean (SD) Mean (SD) Mean (SD) Mean (SD) F (p-value) Age (years) 24.9 (5.4) 24.9 (5.2) 24.9 (5.5) 25.1 (5.6) 1.5 (0.235) Body Mass Index 29.2 (5.1) 29.5 (5.2)* 28.9 (5.0)* 28.4 (4.7)* 61.1 (<0.001)

N N (%) N (%) N (%) X2 p-value Race/Ethnicity White/Non-Hispanic 14539 (71.0) 7589 (74.6) 4206 (66.2) 2376 (68.4) <0.001 Black/Non-Hispanic 1329 (6.5) 537 (5.3) 452 (7.1) 266 (7.7) Hispanic 2876 (14.0) 1364 (13.4) 1048 (16.5) 441 (12.7) Other 1742 (8.5) 683 (6.7) 648 (10.2) 393 (11.3) Marital Status Married 14344 (68.4) 7332 (69.6) 4334 (67.0) 2380 (68.8) 0.003 Single 6613 (31.6) 3208 (30.4) 2130 (33.0) 1078 (31.2) Education Less than High School 1072 (12.0) 696 (11.9) 245 (11.6) 82 (12.1) 0.007 High School Diploma 2474 (27.8) 1679 (28.7) 549 (26.1) 156 (23.0) More than High School 5362 (60.2) 3470 (59.4) 1310 (62.3) 439 (64.8) Insurance Private 16128 (78.9) 8165 (77.6) 4847 (79.9) 2810 (83.7) <0.001 Other 4301 (21.1) 2360 (22.4) 1222 (20.1) 547 (16.3) Birth Attendant Physician 19200 (88.3) 9936 (91.2) 5856 (87.1) 2946 (81.2) <0.001 Midwife 2021 (9.3) 690 (6.3) 690 (10.3) 612 (16.9) Physician/Midwife 515 (2.4) 267 (2.5) 176 (2.6) 71 (2.0) a Percentages are valid. *Significantly different mean scores between all groups.

Figure 2.2 shows the percentage of the sample receiving each number of interventions (0, 1, 2, 3) by dilation at admission. As cervical dilation at admission increased, women received fewer total interventions. This trend occurred regardless of whether women received one intervention (11.4% at 0-3 cm, 8.4% at 4-5 cm, and 5.8% at

6-10 cm), two interventions (24.6% at 0-3 cm, 13.5% at 4-5 cm, and 5.4% at 6-10 cm), or three interventions (14.0% at 0-3 cm, 7.4% at 4-5 cm, and 1.6% at 6-10 cm). The

21 percentage of women receiving no interventions was approximately 2% for women admitted at 0-3 cm and 4-5 cm whereas a greater percentage of women admitted at 6-10 cm received no interventions (3.4%).

Table 2.2. Interventions and delivery mode by dilation at admission 0-3 cm 4-5 cm 6-10 cm n=10943 n=6759 n=3659 Total (51.2%) (31.6%) (17.1%) (n=21858) N (%) N (%) N (%) N (%) Intervention Combinations None 465 (4.4) 449 (7.0) 684 (20.8) 1665 (8.0) Amniotomy 386 (3.6) 473 (7.4) 491 (14.9) 1413 (6.8) Epidural 1728 (16.3) 1097 (17.1) 596 (18.1) 3454 (16.6) Oxytocin 212 (2.0) 146 (2.3) 98 (3.0) 458 (2.2) Amniotomy-Epidural 1804 (17.0) 1673 (26.1) 757 (23.0) 4450 (21.4) Amniotomy-Oxytocin 138 (1.3) 197 (3.1) 94 (2.9) 433 (2.1) Epidural-Oxytocin 3054 (28.8) 870 (13.6) 243 (7.4) 4220 (20.3) Amniotomy-Epidural- 2837 (26.7) 1513 (23.6) 330 (10.0) 4733 (22.7) Oxytocin Delivery Mode Vaginal 9062 (82.8) 6102 (90.3) 3473 (94.9) 18841 (86.2) Cesarean 1879 (17.2) 655 (9.7) 185 (5.1) 3011 (13.8) a Percentages are valid

The relative risk of receiving each intervention combination at 4-5 cm and 6-10 cm dilation at admission compared to 0-3 cm dilation at admission is shown in Table 2.3.

Women were 12% more likely to receive no interventions when admitted at 4-5 cm (RR

1.12, CI95 1.12-1.48) and four times more likely to receive no interventions when admitted at 6-10 cm (RR 4.00, CI95 3.49-4.57) compared to those admitted at 0-3 cm.

Women receiving one intervention were more likely to receive amniotomy when admitted at 4-5 cm dilation (RR 1.79, CI95 1.55, 2.07) and at 6-10 cm dilation (RR 3.41,

CI95 2.93, 3.96) compared to those admitted at 0-3 cm. Dilation at admission did not significantly influence likelihood of receiving epidural or oxytocin except for women admitted at 4-5 cm who were less likely to receive oxytocin (RR 0.78,CI95 0.62-0.97).

Figure 2.2. Percentage of sample receiving number of interventions by dilation at admission

24.6%

Zero

14.0% 13.5%

11.4% One 8.4%

7.4% Two

5.8% 5.4%

3.4% Three

Percentage of Sample Total

2.3%

2.2% 1.6%

0-3cm 4-5cm 6-10cm Cervical Dilation at Admission

Greater dilation at admission significantly increased likelihood of receiving amniotomy- epidural and amniotomy-oxytocin, but decreased likelihood of receiving epidural- oxytocin. Admission at 4-5 cm did not significantly influence the likelihood of receiving amniotomy-epidural-oxytocin. Women admitted at 6-10 cm dilation were 60% less likely to receive amniotomy-epidural-oxytocin (RR 0.40, CI95 0.35-0.46) compared to those admitted at 0-3 cm dilation. Risk ratios adjusted by maternal age, BMI, and comorbidity showed little difference from unadjusted risk ratios (data not shown). Women admitted at

≥ 4 cm cervical dilation had a significantly lower likelihood of having a cesarean birth.

Compared to women admitted at 0-3 cm dilation, those admitted at 4-5 cm dilation were

56% less likely to have cesarean birth (RR 0.44, CI95 0.40-0.49). Women admitted at 6-

10 cm dilation were 80% less likely to have cesarean birth (RR 0.20, CI95 0.17-0.24) compared to those admitted at 0-3 cm.

Table 2.3. Relative risk of interventions and cesarean birth by dilation at admission 4-5 cm Dilation 6-10 cm Dilation RR (CI 95%) RR (CI 95%) No Interventions 1.28 (1.12, 1.48) 4.00 (3.49, 4.57) Amniotomy Only 1.79 (1.55, 2.07) 3.41 (2.93, 3.96) Epidural Only 0.99 (0.91, 1.08) 1.00 (0.90, 1.11) Oxytocin Only 0.78 (0.62, 0.97) 0.92 (0.71, 1.19) Amniotomy-Epidural 1.75 (1.62, 1.89) 1.38 (1.25, 1.53) Amniotomy-Oxytocin 1.75 (1.39, 2.21) 1.41 (1.06, 1.86) Epidural-Oxytocin 0.43 (0.40, 0.47) 0.26 (0.22, 0.30) Amniotomy-Epidural-Oxytocin 0.99 (0.91, 1.07) 0.40 (0.35, 0.46) Cesarean Birth 0.44 (0.40, 0.49) 0.20 (0.17, 0.24) a Referent is 0-3 cm dilation at admission

2.5 DISCUSSION

Summary

This study differs from existing research conducted in the United States in two ways. First, research conducted thus far has examined the relationship between cervical dilation at admission and the use of intrapartum interventions without consideration of the combined use of interventions. Additionally, most studies have defined early labor as less than 4-5 cm,34,36,66 and one study used the term pre-active labor to describe cervical dilation less than 0.5 cm per hour during the first four hours after admission.33 In contrast, this study compared three categories of dilation at admission: 0-3 cm, 4-5 cm, and 6-10 cm. Despite these differences, some comparisons can be made between results from this study and findings from other research. This study found a decreased likelihood of amniotomy prior to 4 cm except when used in combination with oxytocin and epidural.

Similarly, other research has shown a lower likelihood of amniotomy for NTSV women in pre-active labor (OR=0.8, CI95 0.44-1.32)33 as well as for multiparous and nulliparous women admitted prior to 4 cm of dilation (OR=0.8, CI95 0.7-0.8).66 Whereas results from this study showed no effect of dilation at admission on epidural used alone, other

24 research has shown increased use of epidural associated with admission prior to 4 cm for nulliparous women (RR 1.18, CI95 1.13-1.24)36 as well as for multiparous and nulliparous women (OR=2.2, CI95 2.0-2.4).66 Results from this study showed a greater likelihood of oxytocin when used alone for women admitted prior to 4 cm dilation. Other research has also shown increased likelihood of oxytocin for NTSV women admitted in pre-active labor (OR 6.5, CI95 3.43-12.27)33 as well as for nulliparous women admitted prior to 4 cm of dilation (RR 1.56, CI95 1.50-1.63).36 A study examining nulliparous and multiparous women also found that admission prior to 4 cm of dilation was associated with greater likelihood of oxytocin (OR 2.3, CI95 2.1-2.6).66 Results from this study showing that admission prior to 4 cm of dilation was associated with greater likelihood of cesarean birth were consistent with findings from other studies. Likelihood of cesarean birth has been shown to be increased for NTSV women admitted in pre-active labor

(OR=2.6, CI95 1.02-6.37),33 for nulliparous women admitted prior to 4 cm (OR=1.50,

CI95 1.32-1.70),36 and for nulliparous and multiparous women admitted prior to 5 cm of dilation (OR=2.38, CI95 1.4-4.0).34 Only one study found that admission prior to 4 cm of dilation did not have an effect on cesarean birth for nulliparous and multiparous women

(OR=1.0, CI95 0.6-1.8).66

Examining the order in which interventions were applied would provide insight about whether cervical dilation at admission initiates a cascade of interventions that is positively associated with cesarean birth. This analysis was not possible in our study due to large amounts of missing data for timing of intervention application. Petersen et al.

(2011, 2013) examined order and timing of intrapartum interventions in Germany and found that that nulliparous women were more likely to receive epidural anesthesia prior

25 to amniotomy or oxytocin augmentation.52,53 Additionally, epidural was applied at a mean cervical dilation of 2.8 cm. By three hours after the onset of labor, nulliparous women had received the following interventions: amniotomy (8.9%), oxytocin augmentation (8.4%), and epidural anesthesia (10.7%). However, motivations and payment systems are likely to influence practice patterns differently in Germany than in the private payer system in the Unites States. Additionally, results suggest that intervention rates may differ between the United States and Germany. For example, results from this study showed that nearly 90% of women received epidural anesthesia whereas, only 34.2% of nulliparous women received epidural anesthesia in the Petersen et al. (2011, 2013) study. Although timing of interventions has not been examined in the

United States, it is likely that women who are admitted at lower cervical dilations receive interventions sooner than women who present to the hospital in active labor. Women who arrive to the hospital in active labor will likely have a more established contraction pattern and greater cervical dilation, requiring less intervention to encourage further progress toward delivery.

A noteworthy finding in this study is that 13.8% of births occurred by cesarean, and this rate is half the national cesarean birth rate among NTSV women in 2014.59 The overall cesarean birth rate among NTSV women in the Consortium on Safe Labor dataset was 23.9% for all types of admission (e.g., onset of spontaneous labor, induction of labor, pre-labor cesarean). Since women undergoing induction of labor require a minimum number of interventions to initiate labor, this finding suggests that the difference in cesarean birth rates may be related to the timing and sequence of intrapartum interventions. Future research is needed in the United States to examine whether cervical

26 dilation at admission following spontaneous onset of labor influences the timing and sequence of interventions. Additionally, research is needed to examine differences in the timing and sequence of intrapartum interventions following spontaneous onset of labor versus induction of labor and whether these differences influence cesarean birth.

Limitations

A limitation of this study is that data from the Consortium on Safe Labor was collected from births that occurred between 2002-2008 and therefore may not reflect current practice. However, findings in this study provide descriptive data about the use of intrapartum interventions and cesarean birth by cervical dilation at admission in the

United States. This data will serve as a useful comparator for research conducted after

2014 when the American College of Obstetricians and Gynecologist and the Society for

Maternal Fetal Medicine published a joint consensus statement citing 6 cm of cervical dilation as the threshold for active labor.3 An additional limitation is that intrapartum interventions examined in this study were limited to those available in the Consortium on

Safe Labor dataset. Many interventions used to manage labor are not routinely recorded in the electronic medical record. For instance, data was not available for electronic fetal monitoring, a procedure that has been reported as being used in 89% of births68 and may influence cesarean birth by limiting mobility. Interventions shown to reduce cesarean delivery such as non-pharmacological pain management,27 repositioning during labor,71 continuous labor support,72 and oral intake during labor73 were also not available for analysis because these interventions are not routinely documented in the electronic medical record.

Conclusion

Findings from this study show that despite their low-risk nature NTSV women receive multiple interventions during labor. Fewer women admitted in active labor receive interventions during labor, regardless of the total number of interventions applied.

Furthermore, admission after 4 cm of cervical dilation is associated with a lower likelihood of amniotomy, epidural, and oxytocin augmentation applied in combination as well as a lower likelihood of cesarean birth. Based on these results, women should be encouraged to delay admission until active labor to reduce the use of intrapartum interventions and likelihood for cesarean birth. Future research is needed to examine the timing and sequence of interventions to determine whether these factors influence the use of cesarean birth.

Chapter 3: Influence of Hospital and Provider Characteristics on Intrapartum

Interventions and Cesarean Birth in NTSV Women

3.1 ABSTRACT

Objective: To examine the influence of hospital and provider characteristics on the use of amniotomy, epidural, oxytocin, and cesarean birth in low-risk women with spontaneous onset of labor.

Methods: This was a cross-sectional, observational study of 17,443 nulliparous singleton term vertex deliveries that occurred from 2002-2007 across eight hospitals in the

Consortium on Safe Labor.

Results: The overall cesarean birth rate was 13.5% and ranged from 8.8-19.5% across hospitals and from 1-80% across providers. Provider specialty had a significant influence on provider-level cesarean birth rates. The strongest effect was seen in the MFM physicians having more than double the cesarean rate compared to non-MFM physicians

(Mean=0.40 ± 0.20 versus Mean=0.18 ± 0.12) t (15)= -4.17, p=0.001, d=1.33. Female providers had a 22% higher likelihood of using no intrapartum interventions (RR 1.22,

CI95 1.05-1.41) and were half as likely to attend cesarean births (RR 0.5, CI95 0.42-

0.61). Compared to obstetrician/gynecologist physicians, midwives were nearly twice as likely to use no intrapartum interventions (RR 1.81, CI95 1.50-2.19) and were 23% less likely to use amniotomy-epidural-oxytocin (RR 0.77, CI95 0.66-0.91). Family practice physicians had an 18% lower likelihood of using amniotomy-epidural-oxytocin (RR 0.82,

CI95 0.70-0.95) and a 55% lower likelihood of performing cesarean deliveries (RR 0.45,

CI95 0.34-0.58) compared to obstetrician/gynecologist physicians. The only hospital characteristic that significantly influenced the use of intrapartum interventions was

29 availability of an as-needed laborist. Compared to having a laborist available 24/7, an as- needed laborist was associated with a four times higher likelihood of no interventions

(RR 4.27, CI95 1.43-12.70). Hospital type was the only characteristic that was significantly associated with likelihood of cesarean birth, where women delivering at a community teaching hospital had a 31% lower likelihood of cesarean birth compared to women delivering at a university teaching hospital (RR 0.69, CI95 0.68-0.70).

Conclusion: Provider practice type and specialty had a moderate to strong influence on physician-level cesarean birth rates. Provider sex and practice type also had a significant influence on the likelihood of intrapartum intervention use and cesarean birth. These results suggest that standardization is needed to reduce variation of intrapartum care and the use of cesarean birth across providers.

Keywords: hospital, provider, intrapartum interventions, cesarean birth

3.2 INTRODUCTION

The US cesarean birth rate has increased dramatically in recent decades, from

20.7% in 199674 to a current rate of 31.9%.2 This is a public health concern because cesarean birth is associated with increased mortality and morbidity. Women who experience cesarean birth have a four times higher rate of maternal mortality 3 as well as increased risk of blood transfusion, venous thromboembolism, hysterectomy, and placental complications in future pregnancies.5–7,61 Neonates delivered by cesarean birth also have higher rates of morbidity including asthma, type II diabetes mellitus, and obesity.8–12

Efforts to address this trend are focused on preventing the first cesarean birth because 90% of women who experience cesarean birth will deliver by the same route in subsequent pregnancies.17 In particular, prevention is focused on women who are considered low-risk

30 for the procedure, defined as defined as nulliparous, and pregnant with a term singleton, gestation in the vertex position (NTSV).

Research has shown that national cesarean birth rates vary by tenfold across hospitals.16 Despite being low-risk for the procedure, NTSV women have even greater variation, ranging fifteen-fold from 2.4 to 36.5%.16 Research examining physician-level cesarean rates has also found a wide variation across physicians. Evidence has shown that physician-level cesarean birth rates ranged from 3% to 42.3%75–77 and among women undergoing primary cesarean delivery, rates varied from 9.6% to 31.8%.78 However, these studies were conducted 20-30 years ago when cesarean birth rates were much lower and therefore results may not be generalizable to the present. A recent study of nulliparous cesarean birth rates by labor and delivery nurse found a range of 8.3% to

48.0%79, but no current evidence was identified in which physician-level cesarean rates were examined.

In 2013, the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal Fetal Medicine (SMFM) published a joint consensus statement on preventing primary cesarean in which clinical practice patterns were identified as a factor influencing NTSV cesarean birth rates.3 This link suggests that cesarean birth rates vary across hospitals due to differences in practice patterns. In particular, practice patterns may differ with respect to the use of intrapatum interventions such as amniotomy, epidural anesthesia, and oxytocin augmentation. Some research has shown that hospital and provider-level factors influence the use of intrapartum interventions and cesarean birth. Hospital characteristics shown to increase risk of cesarean birth include status as a tertiary center, having the lowest level of nursery care, and having an

31 obstetrics and gynecology residency program.24,80 In contrast, a lower odds of cesarean birth has been associated with the availability of a 24/7 laborist,81 otherwise referred to as an obstetricianist or obstetric hospitalist. Regarding provider characteristics, certified nurse midwives have been shown to use fewer intrapartum interventions than physicians including induction of labor, epidural anesthesia, episiotomy, and instrumental birth.46,47

The purpose of this study was two-fold. The first aim was to examine the influence of provider characteristics on physician-level NTSV cesarean birth rates. The second aim was to examine the influence of hospital and provider characteristics on: (1) the use of amniotomy, epidural anesthesia, and oxytocin augmentation; and (2) cesarean birth in NTSV women.

3.3 METHODS

This was a retrospective, observational study of a subset of participants from the

Eunice Kennedy Shriver National Institute of Child Health and Human Development,

National Institutes of Health, Consortium on Safe Labor (CSL). The CSL was a multisite retrospective cohort study conducted from 2002-2008. Data were collected for 228,438 deliveries from electronic medical records across 12 clinical sites comprised of 19 hospitals, including nine community teaching hospitals, eight university-affiliated teaching hospitals, and two non-teaching community hospitals. Hospital- and provider- level data were collected through a survey administered at each clinical site. The Data

Coordinating Center of the CSL confirmed that data were an accurate representation of the medical record by conducting random verification of critical variables and selected confirmation of missing or anomalous data.

The analytic file for this study included women admitted in spontaneous labor who were nulliparous and pregnant at term gestation with a single fetus in the vertex position (NTSV) (Figure 3.1). Eight hospitals were excluded due to completely missing data for one or more intervention variables of primary interest. Another three hospitals

Figure 3.1. Sample selection (n=17,443) were excluded because 33-100% of data were missing for provider characteristics. The

33 resulting analytic file included 17,443 NTSV deliveries attended by 591 providers across eight hospitals from 2002-2007.

Outcomes included use of intrapartum interventions (e.g., amniotomy, epidural anesthesia, oxytocin augmentation) and mode of birth (e.g., cesarean, vaginal). Based on intra-class correlations for hospital-level effects (amniotomy=0.01, epidural=0.19, oxytocin=0.15, cesarean=0.02) and provider-level effects (amniotomy=0.01, epidural=0.21, oxytocin=0.16, cesarean=0.15), a multilevel approach was selected.

Required sample size was calculated a priori based on published effect sizes ranging from

0.2 to 3.4 for the influence of hospital and provider characteristics on intrapartum interventions and cesarean birth.24,42,47,81,82 For most relationships examined in this study the maximum required sample size was estimated at n=10,054 to detect an effect at 80% power with alpha level (two-sided)=0.05. Except for required sample sizes to detect an effect for provider age on cesarean birth and to detect an effect of midwifery care on the use of oxytocin augmentation, the sample size of n=17,443 was determined to be adequate for most relationships examined in this study.

Descriptive statistics were used to examine maternal, provider, and hospital characteristics as well as the use of intrapartum interventions and cesarean birth across hospitals and providers. Of 592 unique providers in the data dataset, 157 providers attended fewer than 10 deliveries. Therefore, providers with low birth volumes were excluded from provider-level cesarean birth rate calculations, by excluding those in the lowest quartile for number of deliveries (<8 deliveries). To ensure that providers with nonsurgical practices (i.e., midwives) were excluded from the analyses, those with a 0% cesarean rate were also excluded from provider-level cesarean rate analyses. These

34 exclusions resulted in calculation of cesarean birth rates for n=337 physicians.

Independent t-tests were calculated to examine physician-level cesarean birth rates by provider characteristics using p<0.20. Generalized linear mixed modeling was conducted to examine the influence of hospital and provider characteristics on intrapartum interventions and cesarean birth. Models were adjusted by accounting for maternal age and body mass index (BMI) based on evidence that these factors are associated with cesarean delivery.21,22,70 Data were obtained after the researchers signed a data use agreement. The study was deemed non-human subjects research by the University of

Maryland Institutional Review Board because the dataset is de-identified. Statistical analyses were conducted using SAS version 9.4.

3.4 RESULTS

Of the eight hospitals included in the study, two were university-affiliated teaching hospitals, four were teaching community hospitals, and two were non-teaching community hospitals. Two hospitals were secondary level obstetric care and the remainder were tertiary level of care. One hospital had no neonatal intensive care unit

(NICU), two had a level two specialty NICU, and the rest had a level three subspecialty

NICU. The number of deliveries that occurred at each hospital in 2006 ranged from 2251 to 6883 with a mean of 4208 ( 1153). All hospitals had 24-hour coverage by an anesthesiologist and an obstetric attending physician. All but two hospitals also had 24- hour coverage by a laborist. Two hospitals had maternal fetal medicine physicians and five had midwives.

Table 3.1 shows maternal and provider characteristics. There were 591 providers across the eight hospitals in the study. Mean age of providers was 49.0 years ( 9.6) and the majority were male (61.4%). The majority of providers were in private practice

Table 3.1. Provider and maternal characteristics Provider Characteristics (n=591) Mean ± SD Age (years) 49.0 ± 9.6 Sex N (%) Male 10651 (61.4) Female 6686 (38.6) Practice type Private 14340 (82.5) University faculty 1762 (10.1) Clinic 475 (2.7) Other 804 (4.6) Specialty Obstetrician/Gynecologist 13399 (77.1) Maternal fetal medicine 299 (1.7) Family practice 1479 (8.5) Midwife 1814 (10.4) Other 390 (2.2) Maternal Characteristics (n=17,443) Mean (SD) Age (years) 25.1 ± 5.6 N (%) Race/Ethnicity White/Non-Hispanic 11821 (73.2) Black/Non-Hispanic 1100 (6.8) Hispanic 2430 (15.1) Other 790 (4.9) Marital Status Married 11088 (68.7) Single 5459 (33.8) Education Less than High School 1065 (12.0) High School Diploma 2474 (27.8) More than High School 5357 (60.2) Insurance Private 12072 (74.8) Public 3935 (24.4)

(82.5%). The most common specialty across hospitals was obstetricians/gynecologists

(OB/GYN) (77.1%), followed by midwives (10.4%) and family practice physicians

(8.5%). Mean maternal age was 25.1 years ( 5.6) and the majority of women were Non-

Hispanic White (73.2%). Most women were married (68.7%), had more than a high school education (60.2%), and had private health insurance (74.8%).

Clinical practices varied across hospitals (data not shown). Physicians attended

89.6% of deliveries and 7.5% were attended by midwives. Both a physician and midwife attended the remaining 3.0% of deliveries. Approximately half of women received amniotomy (52.3%) and the rate varied from 48.5% to 59.8% across hospitals. Half of women received oxytocin augmentation (49.6%) and the rate ranged from 24.0% to

83.2% across hospitals. The vast majority of women received epidural anesthesia (82.1%) and the rate ranged from 59.8% to 95.3% across hospitals.

Hospital- and physician-level cesarean birth rates are shown by hospital in Figure

3.2. Hospital-level cesarean birth rates ranged from 8.8% to 19.5%. Cesarean birth rates ranged from 1% to 80% for the n=337 physicians included in the analysis. The majority of physicians had cesarean rates ranging from 2% to 40%. Hospital 6 had the widest range of physician-level cesarean rates, from 2% to 80%. Hospital 1 had the smallest range, from 8% to 30%, as well as the fewest number of physicians (n=14). Provider characteristics that had a significant influence on provider-level cesarean rates were sex, practice type as a private practitioner, practice type as a university faculty, MFM specialty, and family practice specialty (Table 3.2). Female providers had a lower cesarean birth rate (Mean=0.16 ± 0.10 versus Mean=0.20 ± 0.14), t (115) = 2.75, p=0.006, d=0.33. Private practice physicians had a lower cesarean rate (Mean=0.18 ±

90%

80%

70%

60%

50%

40%

30%

20%

10%

0% 0 1 2 3 4 5 6 7 8 9 Hospital

Figure 3.2. Hospital and physician-level cesarean birth rate by hospital. a Each red represents one hospital. b Each grey dot represents one physician.

0.12),Figure t (275)=2.37,2.1. Coyle and p=0.021,Battle vers iond=0.34 of the compared Donabedian to Model nonFigure-private 3.3. Providerpractice-level physicians cesarean birth rate by hospital (n=337). a Each dot represents one provider. (Mean=0.23 ± 0.17). University faculty had a higher cesarean rate (Mean=0.27 ± 0.18), t

(30)=-2.59, p=0.015, d=0.59 compared to non-university faculty (Mean=0.18 ± 0.12).

MFM physicians had more than double the cesarean rate compared to non-MFM physicians and this relationship had the largest effect size of any provider characteristic examined (Mean=0.40 ± 0.20 versus Mean=0.18 ± 0.12), t (15)=-4.17, p=0.001, d=1.33.

Family practice physicians had a lower cesarean rate compared to non-family practice physicians (Mean=0.13 ± 0.12 versus Mean=0.20 ± 0.13), t (42)=2.87, p=0.004, d=0.48.

The results of generalized linear mixed models examining the relationships between provider characteristics and interventions as well as between provider characteristics and cesarean birth are presented in Table 3.3. Models adjusting for

38 maternal age and BMI showed little to no difference in results (data not shown). Female providers were 22% more likely to use no interventions (RR 1.22, CI95 1.05-1.41) and were less likely to use amniotomy (RR 0.89, CI95 0.82-0.96) and epidural (RR 0.82,

CI95 0.72-0.93). Female providers were also half as likely to attend cesarean births (RR

0.50, CI95 0.42-0.61). In comparison with private practice physicians, clinic physicians were 42% less likely to use epidural (RR 0.58, CI95 0.42-0.79) and were half as likely to attend cesarean births (RR 0.49, CI95 0.28-0.83). Physicians in other practice types (i.e., federal, state, or county

Table 3.2. T-tests comparing physician-level cesarean birth rates by physician characteristics Cesarean Rate M SD n t-value df p-value Cohen’s d Sex Female 0.16 0.10 115 2.75c 297 0.006 0.33 Male 0.20 0.14 218 Practice Type Private Yes 0.18 0.12 275 2.37c 71.8 0.021 0.34 No 0.23 0.17 60 University Faculty Yes 0.27 0.18 30 -2.59c 31.7 0.015 0.59 No 0.18 0.12 305 Clinic Physician Yes 0.20 0.09 9 -0.29 333 0.772 0.09 No 0.19 0.13 326 Other Yes 0.20 0.18 21 -0.28c 21.5 0.785 0.06 No 0.19 0.13 314 Specialty type OB/GYN a Yes 0.19 0.12 261 0.40c 92.15 0.693 0.05 No 0.19 0.17 74 MFM b Yes 0.40 0.20 15 -4.17c 14.4 0.001 1.33 No 0.18 0.12 320 Family Practice Yes 0.13 0.12 42 2.87 333 0.004 0.48 No 0.20 0.13 293 a OB/GYN is obstetrician/gynecologist b MFM is maternal fetal medicine c Equal variances not assumed

39 employee) were 31% less likely to use epidural (RR 0.69, CI95 0.52-0.92). There were also many significant relationships between provider specialty and the use of intrapartum interventions and cesarean birth. Compared to OB/GYN specialists, maternal-fetal medicine (MFM) specialists were 55% more likely to use no interventions (RR 1.55,

CI95 1.07-2.25) and amniotomy (RR 1.35, CI95 1.04-1.75). However, MFM specialists were less likely to use epidural (RR 0.65, CI95 0.47-0.90). Additionally, MFM physicians were nearly twice as likely as OB/GYN specialists to perform cesarean deliveries (RR 1.95, CI95 1.35-2.82). In comparison with OB/GYN specialists, family practice physicians were less likely to use epidural (RR 0.73, CI95 0.58-0.92), oxytocin

(RR 0.86, CI95 0.74-0.99), and the combination of amniotomy-epidural-oxytocin (RR

0.82, CI95 0.70-0.95). Additionally, family practice physicians were 55% less likely to perform cesarean deliveries (RR 0.45, CI95 0.34-0.58). Compared to OB/GYN specialists, midwives were more likely to apply no interventions (RR 1.81, CI95 1.50-

2.19). Midwives were less likely to use amniotomy (RR 0.86, CI95 0.76-0.97), epidural

(RR 0.48, CI95 0.41-0.57), oxytocin (RR 0.78, CI95 0.68-0.90) and the combination of amniotomy-epidural-oxytocin (RR 0.77, CI95 0.66-0.91). Other specialties (i.e., reproductive endocrinologists, urologist gynecologists, fellows, and resident physicians) were more likely than OB/GYN specialists to use amniotomy (RR 1.40, CI95 1.11-1.77) but less likely to use epidural (RR 0.68, CI95 0.51-0.90). Other specialists were also less likely than OB/GYN specialists to perform cesarean deliveries (RR 0.65, CI95 0.43-

0.99).

Few hospital characteristics were significantly associated with the use of intrapartum interventions and cesarean birth (data not shown). Moreover, adjusting for

40 maternal age and BMI had little effect on results. Women delivering at a community teaching hospital had a 31% lower likelihood of cesarean birth compared to women delivering at a university teaching hospital (RR 0.69, CI95 0.68-0.70). In comparison with having a 24/7 laborist available, having a laborist on an as-needed basis was associated with four times greater likelihood of no interventions (RR 4.27, CI95 1.43-

12.7). However, having an as-needed laborist was associated with a lower likelihood of amniotomy (RR 0.96, CI95 0.72-1.28), epidural (RR 0.19, CI95 0.06-0.63), and oxytocin

(RR 0.24, CI95 0.07-0.79), and use of amniotomy-oxytocin-epidural (RR 0.27, CI95

0.12-0.59).

by by provider

s s

intrapartum intervention

Relative risk Relative of

3. 3.

Table characteristics

3.5 DISCUSSION

Summary

Results showed that providers had a greater variation in cesarean rates (1%-80%) than the eight hospitals included in the study (8.8% to 19.5%). The overall cesarean birth rate of 13.5% in this study is lower than the national NTSV rate of 26% in 2014.59

However, the overall cesarean birth rate was 23.9% for all NTSV women in the

Consortium on Safe Labor regardless of reason for admission (e.g., spontaneous onset of labor, induction of labor, pre-labor cesarean). Therefore, the low cesarean birth rate in this study may have been due to exclusion of women undergoing induction of labor and pre-labor cesarean. Despite the effect of excluding women whose labor was induced, the hospital-level cesarean birth rates in this study were within the 2.4% to 47.3% range that has been observed in other studies examining NTSV deliveries in the United

States.16,24,83–85

Physician-level cesarean birth rates varied by eighty-fold in this study. This range was much greater than the 3% to 31.8% variation that was previously observed in studies conducted 20-30 years ago.75–77 Although data from this study were from 2002-2007, no other more recent study that has examined provider-level cesarean delivery rates was identified. In addition to the results of this study showing a wide variation across hospitals, physician-level cesarean birth rates varied widely within hospitals. Some of this variation may be explained by the influence of physician characteristics, such as sex, practice type, and specialty, on cesarean birth rates. For example, findings that cesarean delivery rates were higher among university faculty physicians show that these physicians may be practicing differently than others. A higher rate among MFM

43 physicians may be expected given that these physicians specialize in care of high-risk pregnancies whereas a lower cesarean rate among family practice physicians may reflect care of a lower risk population. These results suggest that for providers who do not specialize in high-risk pregnancies, practice patterns may be a modifiable factor to reduce cesarean birth rates, particularly among NTSV women.

The influence of provider characteristics on the use of intrapartum interventions has only been examined with respect to differences in midwife-led care versus other models of care. A Cochrane systematic review found that in comparison with other models of care, midwife-led care was associated with a lower likelihood of amniotomy

(RR 0.80, CI95 0.66-0.98), epidural (RR 0.83, CI95 0.76-0.90), and oxytocin augmentation (RR 0.89, CI95 0.79-1.01).44 Findings in this study were similar, showing that midwives were less likely to use amniotomy (RR 0.86, CI95 0.76-0.97), epidural

(RR 0.48, CI95 0.41-0.57), oxytocin (RR 0.78, CI95 0.68-0.90) compared to OB/GYN specialists.

Regarding the association between provider characteristics and the use of cesarean birth, agreement between results in this study and the existing evidence was mixed. Two studies showed similar findings that male providers had twice the likelihood of performing cesarean deliveries. Mitler et al. found that male providers had a 38% higher likelihood of cesarean birth (OR 1.38, CI95 1.00-1.88).45 A study by Haberman et al. using data from all 19 hospitals in the Consortium on Safe Labor and including women who were induced showed that male providers had a 21% higher likelihood of cesarean birth (RR 1.21, CI95 1.09-1.16).43 Haberman et al. also found that university faculty had a higher likelihood of cesarean birth (RR 1.13, CI95 1.09-1.16) compared to

44 private practice physicians. In contrast, findings in this study showed that university faculty had a lower likelihood of cesarean birth in comparison with private practice physicians (RR 0.91, CI95 0.65-1.28). This difference may be due to sample selection where Haberman et al. included eight university-affiliated teaching hospitals and this study included two university hospitals. Additionally, evidence is mixed regarding the influence of induction of labor on cesarean birth. By including women who were induced, Haberman et al. may have introduced a confounder that was not present in this study.

The findings in this study showing significant relationships between hospital characteristics and intrapartum interventions as well as between hospital characteristics and cesarean birth have not been examined elsewhere in the literature. Results in this study show that women delivering at community teaching hospitals had a 30% lower likelihood (RR 0.69, 0.68-0.70) of cesarean birth compared to university-affiliated teaching hospitals. The most similar study found that compared to a community hospital, there was a three times higher likelihood of cesarean birth at a tertiary level hospital (OR

3.4, OR 95 2.1-5.4). In this study, having a laborist available on an as needed basis was associated with a 34% lower likelihood of cesarean birth (RR 0.66, CI95 0.40-1.11) although results were not found to be significant. A similar study by Iriye et al. found that having a full-time laborist was associated with a 33% lower likelihood of cesarean birth

(OR 0.73, CI95 0.64-0.83). As discussed by Iriye et al., the traditional hospitalist model has extended into labor and delivery in the last decade and there are several different obstetrical hospitalist (i.e. laborist) models.41 Thus, it is difficult to differentiate among these types of care across hospitals.

Limitations

Due to the use of a convenience sample, the results of this study have limited generalizability. Although associations may be drawn from these observational data regarding the relationship between provider characteristics and clinical practice patterns, it is not possible to rule out confounding variables that may influence these decisions. For example, some proportion of women in the study would require cesarean birth to achieve optimal maternal and neonatal outcomes regardless of hospital or provider factors that may influence this decision. Patient preference may also play a role, particularly with respect to the use of intrapartum interventions to manage pain or augment labor in order to expedite birth. Additionally, hospital policies and nursing care may have also influenced the use of interventions and the decision to proceed with cesarean birth.

Another limitation of this study is that some assumptions were made due to constraints of using existing data. Although several providers may have participated in the management of labor, these data were not available in the dataset. The provider attending delivery was assumed to also be the provider who managed labor, however this attribution may not be accurate due to handoff of care over the course of labor.

Researchers examining the link between labor nurses and cesarean birth have acknowledged a similar challenge where nurses who are attributed to a cesarean birth may not have influenced the outcome to a greater extent than other nurses involved in care.79 A prospective study design is needed to collect data that accounts for changes in provider coverage over the course of labor.

Conclusion

This observational study shows that there is wide variation in physician-level cesarean birth rates within hospitals. However, provider characteristics do not fully explain the variation in rates. Differences in practice patterns with regard to the use of intrapartum interventions may explain some variation across provider specialties.

Research is needed to further explore provider influence on cesarean birth. In particular, the development of more advanced methods to account for provider attribution would facilitate better modeling of provider influence on the use of intrapartum interventions.

Having a clearer understanding of differences in provider practice may explain the variation in physician-level cesarean birth rates.

Chapter 4: Influence of Amniotomy, Epidural Anesthesia, and Oxytocin

Augmentation on Cesarean Birth in Low-Risk Pregnancies

4.1 ABSTRACT

Purpose: Although some research has examined the influence of intrapartum interventions on cesarean birth, most evidence has only focused on interventions used individually or in pairs. The purpose of this study was to examine the influence of amniotomy, epidural anesthesia, and oxytocin augmentation used individually and in combination on cesarean birth in low-risk women in spontaneous labor.

Methods: This was a retrospective observational study of 26,259 nulliparous, singleton, term gestation, vertex births (NTSV) that occurred from 2002-2007 across eleven hospitals in the Consortium on Safe Labor.

Results: Women who delivered vaginally more often received epidural only (15.1%) compared to those who underwent cesarean birth (6.7%). In contrast, women receiving epidural-oxytocin more often delivered by cesarean birth (37.5% versus 28.0% vaginal birth). The same trend was noted for women who received amniotomy-epidural- anesthesia (38.0% cesarean birth versus 29.4% vaginal birth). Compared with women who received no interventions, those receiving amniotomy only (RR 1.59, CI95 1.28-

1.98) and oxytocin only (RR 1.64, CI95 1.22-2.21) had a significantly increased likelihood of cesarean birth. Likelihood of cesarean birth increased when amniotomy and oxytocin were paired with additional interventions. Women who received all three interventions had nearly twice the likelihood of cesarean birth compared to those who received no interventions (RR 1.84, CI95 1.53-2.21).

Conclusion: Likelihood of cesarean birth is increased when amniotomy, epidural

48 anesthesia, and oxytocin augmentation are applied as a pair or a combination of all three interventions. Given the increased risk of cesarean birth associated with these interventions, the combined use of intrapartum interventions should be carefully considered relative to the risk of cesarean birth.

Keywords: intrapartum interventions, cesarean birth, low-risk pregnancy

4.2 INTRODUCTION

The current cesarean birth rate of 31.9% in the United States2 exceeds the threshold to achieve optimal maternal and neonatal outcomes. Studies examining international cesarean birth rates have shown that maternal and neonatal mortality do not decline at cesarean rates above 10-19%.13,14 Even among low-risk women, defined as nulliparous and pregnant at term gestation with a single fetus in the vertex position

(NTSV), the national cesarean rate of 26%59 exceeds the Healthy People 2020 goal of

23.9%.86 Although factors such as older maternal age and obesity are positively associated with cesarean birth,21,22,70 these factors do not explain a tenfold variation in cesarean rates across hospitals.16,83,87 Among NTSV women in particular, cesarean birth rates vary fifteen-fold across hospitals despite that lower variation would be expected due to a lower clinical risk.16 Some research suggests that variation in cesarean birth rates is attributable to differences in provider practice patterns.16,85,88,89

One area where practice patterns may differ is the use of intrapartum interventions such as amniotomy, epidural analgesia, and oxytocin augmentation. A small body of literature has shown that admission to the hospital may initiate a cascade of interventions where one intervention leads to the next, resulting in higher likelihood of cesarean birth.30,31,67 Multiple Cochrane systematic reviews have explored the effect of one or two

49 intrapartum interventions on cesarean birth but results differ based on whether the review examined a single intervention or a pair of interventions. For instance, early amniotomy is associated with an increased likelihood of cesarean birth48 but early amniotomy combined with early oxytocin reduced the likelihood of cesarean birth.49 Similarly, the use of epidural showed a slight increase in the likelihood of cesarean birth,50 but oxytocin augmentation in women also receiving epidural anesthesia showed a decreased likelihood of cesarean birth.51

Although existing literature provides insights about the influence of interventions used individually or in pairs on cesarean birth, evidence shows that the majority of women in the United States receive three or more intrapartum interventions.68 Evidence is lacking to explain the influence of the combined use of intrapartum interventions on cesarean birth. Additionally, most existing research examining the relationship between intrapartum interventions and cesarean birth is not focused on low-risk NTSV women.

The objective of this study was to examine the influence of amniotomy, epidural anesthesia, and oxytocin augmentation used individually and in combination on cesarean birth in NTSV women with spontaneous onset of labor.

4.3 METHODS

This study used data from the Consortium on Safe Labor (CSL), a retrospective, multi-center observational study from the Eunice Kennedy Shriver National Institute of

Child Health and Human Development of the National Institutes of Health. The CSL collected data for 228,438 births across 19 hospitals in the United States from 2002-2008, including nine teaching hospitals, eight university-affiliated teaching hospitals, and two non-teaching community hospitals. Data were extracted from the electronic medical

50 record for maternal demographics, prenatal history, labor and delivery events, and maternal and newborn delivery outcomes.

Figure 1 shows the exclusion criteria used to create the analytic file for this study.

The following exclusion criteria were applied: spontaneous rupture of membranes without onset of labor, induction of labor, or pre-labor cesarean; multiparity; preterm

(<37 weeks), post-term (>42 weeks), or still birth; multiple gestation; and non-vertex fetal position. Eight hospitals were excluded due to completely missing data for one or more intrapartum intervention variables of interest. The resulting analytic file included

26,259 NTSV deliveries that occurred across 11 hospitals from 2002-2007.

Intra-class correlations (ICC) were calculated to account for possible clustering effects at the hospital and provider levels. Based on intra-class correlations of 0.15 for the hospital-level effect and 0.26 for the provider-level effect, a multilevel approach was selected. Using intra-class correlation results, design effects were found to be 5.59 for hospital-level clusters and 7.2 for provider-level clusters. Required sample size was calculated a priori based on published effect sizes for the influence of amniotomy

(RR=1.15), epidural (RR=1.1), oxytocin (RR=2.18), amniotomy-oxytocin (RR=0.89), and epidural-oxytocin (RR=0.95) on cesarean birth.48–51,90 Except for two relationships

(epidural only and cesarean birth, epidural-oxytocin and cesarean birth) maximum required sample size was estimated at n=26071 to detect an effect at 80% power with alpha level (two-sided)=0.05. Therefore, the sample size of n=21,858 was determined to be adequate to detect an effect for most relationships examined in this study.

Chi-square and independent t-tests were performed to compare groups by mode of delivery (e.g. cesarean versus vaginal). P-values <0.05 were considered strong evidence

51 against the null hypothesis. Generalized linear mixed modeling was conducted to examine the relationship between intrapartum interventions used individually and in

Figure 4.1. Sample selection (n=26,259) combination with cesarean birth. Based on evidence that maternal age and body mass

52 index (BMI) are associated with cesarean delivery,21,22,70 adjusted models were also calculated to account for these covariates. Data analyses were conducted using SAS version 9.4.

4.4 RESULTS

Table 4.1 describes characteristics of the sample by mode of delivery. Of the

26,259 deliveries in this study, n=3,596 (13.7%) occurred by cesarean birth. Women who delivered by cesarean were on average two years older (Mean 26.26 years ± 6.0) than women who delivered vaginally (Mean 24.22 years ± 5.3) (p<0.0001). Women who delivered by cesarean also had a greater body mass index (BMI) (Mean 31.84 ± 6.4) compared to women who delivered vaginally (Mean 29.12 ± 5.1) (p<0.0001). The majority of women in both groups were White/non-Hispanic, but there was a significantly higher percentage of White/non-Hispanic women in the vaginal delivery group (64.0%) compared to the cesarean group (58.9%) (p<0.0001). There were significantly more Black/non-Hispanic women in the cesarean birth group (16.6%) compared to the vaginal delivery group (12.5%) (p<0.0001). The majority of women were married, with similar rates in the vaginal delivery group (61.1%) and the cesarean birth group (61.2%). The percentage of divorced women in the cesarean birth group

(1.1%) was significantly greater compared to the vaginal delivery group (0.7%) (p=0.01).

In both groups the majority had more than a high school education and private insurance.

Figure 4.2 shows the percentage of women who received each combination of interventions by delivery mode, where the denominators are the total number of women in the vaginal birth group and total number of women in the cesarean birth group, respectively. Among all possible combinations of interventions, amniotomy-epidural-

53 oxytocin was applied most often regardless of delivery mode. A greater percentage of women in the vaginal birth group received no interventions (3.6%) compared to the cesarean birth group (1.7%). A greater proportion of women in the vaginal birth group also received epidural only (15.1%) compared to those in the cesarean birth group

(6.7%). In contrast, a higher proportion of women in the cesarean birth group received epidural-oxytocin (37.5%) compared with those in the vaginal birth group (28.0%). There

Table 4.1. Demographic characteristics by delivery mode (n=26,259) Vaginal Cesarean n=22656 n=3596 (86.3%) (13.7%) Paired t-test Mean (SD) Mean (SD) (p-value) Age (years) 24.22 (5.3) 26.26 (6.0) <0.0001 Body Mass Index 29.12 (5.1) 31.84 (6.4) <0.0001

Chi-squared N (%) N (%) (p-value) Race/Ethnicity White/Non-Hispanic 13709 (64.0) 2025 (58.9) <0.0001 Black/Non-Hispanic 2677 (12.5) 571 (16.6) <0.0001 Hispanic 3294 (15.4) 506 (14.7) 0.33 Other 1756 (8.2) 334 (9.7) <0.001 Marital Status Married 13198 (61.1) 2117 (61.2) 0.91 Divorced 140 (0.7) 37 (1.1) 0.01 Single 8281 (38.3) 1308 (37.8) 0.56 Education Less than High School 1389 (15.3) 178 (13.1) 0.03 High School Diploma 2501 (27.6) 422 (31.0) 0.01 More than High School 5165 (57.0) 761 (55.9) 0.43 Insurance Private 14855 (70.1) 2444 (72.4) <0.001 Public 6339 (29.9) 930 (27.6) <0.001 a Percentages are valid

54 was also a higher proportion of women in the cesarean birth group that received amniotomy-epidural-anesthesia (38.0%) compared with the vaginal birth group (29.4%).

38.0%

37.5%

29.4%

28.0%

19.2%

15.1%

Percentage by Percentage by Delivery Mode 11.0% Vaginal

6.7% Cesarean

4.1%

3.6%

2.8%

1.7%

1.0%

0.7%

0.6% 0.3%

Figure 4.2. Intrapartum interventions by delivery mode

Table 4.2 shows the relative risk of cesarean birth associated with each combination of intrapartum interventions. Models adjusting for maternal age and BMI are not shown as there was little difference when accounting for these variables. Compared with women receiving no interventions, those receiving any combination of interventions had an 18% to 93% increased likelihood of having a cesarean birth. The relative risk of cesarean birth rose as the number of interventions increased from the application of a single intervention to the application of a pair of interventions. For example, women

55 receiving amniotomy only had a 59% increased likelihood of cesarean birth (RR 1.59,

CI95 1.28-1.98) whereas women receiving amniotomy-epidural (RR 1.64, CI95 1.37-

1.96) or amniotomy-oxytocin (1.91, CI95 1.40-2.60) had a greater likelihood of cesarean birth. This trend was also shown in women receiving epidural only (RR 1.18, CI95 0.98-

1.42) compared to those receiving amniotomy-epidural (RR 1.64, CI95 1.37-1.96) or epidural-oxytocin (RR 1.93, CI95 1.61-2.31). Similarly, women who received oxytocin only had a lower likelihood of cesarean birth (RR 1.64, CI95 1.22-2.21) compared with those receiving amniotomy-oxytocin (RR 1.91, CI95 1.40-2.31) or epidural-oxytocin (RR

1.93, CI95 1.61-2.31). Models adjusting for maternal age and BMI showed little to no difference in results (data not shown).

Table 4.2. Relative risk of cesarean birth by intrapartum interventions N (%) RR (CI 95%) No Interventions 2248 (9.1) 1.0 Amniotomy Only 1645 (6.7) 1.59 (1.28-1.98) Epidural Only 4601 (18.7) 1.18 (0.98-1.42) Oxytocin Only 600 (2.4) 1.64 (1.22-2.21) Amniotomy-Epidural 4870 (19.8) 1.64 (1.37-1.96) Amniotomy-Oxytocin 458 (1.9) 1.91 (1.40-2.60) Epidural-Oxytocin 5256 (21.3) 1.93 (1.61-2.31) Amniotomy-Epidural-Oxytocin 4967 (20.2) 1.84 (1.53-2.21)

4.5 DISCUSSION

Summary

Despite being a low-risk cohort with spontaneous onset of labor, only 3.6% of women who delivered vaginally received none of the interventions of interest and this percentage was even lower among cesarean births (1.7%). No studies were identified that have examined national rates of intrapartum intervention use in NTSV women in the

United States. However, a nationally representative survey conducted in 2013 found that the majority of women reported receiving multiple intrapartum interventions, including continuous electronic fetal monitoring (89%), epidural anesthesia (62%), and exogenous oxytocin (50%).37 Similar to these survey results, findings in this study showed that epidural was the most frequently applied intervention, both as a single intervention and in combination with other interventions. High frequency of epidural use might be expected given the position of the American College of Obstetricians and Gynecologists (ACOG) that women in labor in the hospital setting should receive pharmacologic analgesia upon request.91 The finding that the vast majority of women received two or more interventions shows that in addition to frequent use of epidural for pain management, labor was routinely augmented either by amniotomy or oxytocin infusion. About half of women received augmentation by amniotomy or oxytocin, and approximately 20% received both amniotomy and oxytocin. It is noteworthy that deliveries in this dataset occurred prior to the 2017 ACOG position statement that discourages routine amniotomy in low-risk women with normally progressing labor unless the intervention is required for internal fetal monitoring.92 Although the births that occurred in this sample took place from 2002-

2007, this study provides benchmark data that can serve as a comparison for future measurement of the prevalence of intrapartum interventions such as amniotomy in low- risk women.

This study showed that likelihood of cesarean birth varied depending on the type and combination of intrapartum interventions. Results showing that epidural was associated with a small but non-significant increased likelihood of cesarean birth (RR

1.18, CI95 0.98-1.42) are similar to results from a systematic review that showed the

57 same relationship (RR 1.10, CI95 0.97, 1.25). Whereas in this study epidural-oxytocin was associated with an even greater likelihood of cesarean birth (RR 1.93, CI95 1.61-

2.31), a systematic review found that women receiving epidural-oxytocin had a decreased likelihood of cesarean birth (RR 0.95, CI95 0.42-2.12).51 In this study, amniotomy alone was associated with an increased likelihood of cesarean birth (RR 1.59, CI95 1.28-1.98).

These results are similar to the findings of a systematic review examining the same relationship (RR 1.15, CI95 0.88-1.51).48 In contrast, findings in this study showed a greater increased likelihood of cesarean birth associated with amniotomy-oxytocin (RR

1.91, CI95 1.40-2.60) whereas a systematic review found that early amniotomy combined with early oxytocin reduced the risk of cesarean birth (RR 0.89, CI95 0.79, 1.01).49 The sequence of interventions was not analyzed in this study due to large amounts of missing data for the timing of intervention initiation. Without accounting for sequence of interventions, it is difficult to determine whether interventions were used to address poor labor progression or whether one intervention led to the next, resulting in an increased likelihood of cesarean birth.

Research examining the combined use of amniotomy, epidural anesthesia, and oxytocin augmentation is limited to studies conducted outside of the United States. Tracy et al. (2007)31 conducted a cross-sectional study of a large cohort (n=753,895) of nulliparous and multiparous women in Australia to examine the association between interventions used during labor (e.g., epidural and oxytocin) and mode of delivery (e.g., operative vaginal delivery and cesarean delivery). Unlike in this study, in which induction of labor was an exclusion criterion, Tracy et al. (2007) grouped women receiving oxytocin augmentation with those receiving oxytocin for induction of labor.

The authors found that 71.2% of nulliparous women received at least one intervention in comparison with 91% of women in this study. Nearly one-third of women received epidural-oxytocin and another 9.6% of women received epidural only. In contrast, findings in this study showed that 21.3% of women received oxytocin-epidural and

18.7% received epidural only. Tracy et al. (2007) also found that 15.5% of nulliparous women had a cesarean birth. The cesarean rate of 13.8% in this study was similar to that of Tracey et al. (2007), but low compared to the national NTSV cesarean birth rate of

26% in 2014.59 Whereas Tracy et al. (2007) included both women with spontaneous onset of labor and induction of labor, the sample in this study included only women with spontaneous onset of labor. It should be noted that the overall NTSV cesarean birth rate in the Consortium on Safe Labor was 23.9% regardless of type of admission (e.g., spontaneous onset of labor, induction of labor, pre-labor cesarean).

In contrast with results in this study, research conducted in Germany by Petersen et al.53 reflects a lower intervention approach during the intrapartum period. Petersen et al. 53 conducted a longitudinal multi-center cohort study of nulliparous and multiparous women (n=3,955) in Germany to examine the association between intrapartum interventions (e.g., amniotomy, epidural and oxytocin augmentation) and labor length and mode of delivery. The authors found that 73.2% of nulliparous women received at least one intrapartum intervention whereas 91% of women in this study received at least one intervention. In contrast with findings in this study showing that epidural was the most commonly used intervention overall (80%), Petersen et al.53 found that oxytocin augmentation was the most frequently applied intervention among nulliparous women

(52.6%), followed by amniotomy (34.5%) and epidural anesthesia (34.2%). Petersen et

59 al. reported a 17.8% cesarean delivery rate for nulliparous women in their study, however they did not differentiate what proportion of these women underwent induction versus those who presented in spontaneous labor.

Limitations

Several limitations of this study must be acknowledged. First, the births in this dataset occurred from 2002-2007 and therefore may not reflect current practice. Despite this limitation, this study fills a critical gap where previous research has not examined the relationship between the use of multiple interventions and likelihood of cesarean birth.

Having a greater understanding of the cumulative effect of multiple interventions is necessary because evidence shows that the majority of women in the United States receive multiple interventions.93

A second limitation is that several possible confounding variables that may influence the likelihood of cesarean birth were not accounted for in this study. For example, some interventions have been shown in the literature to decrease the likelihood of cesarean birth, including the use of non-pharmacological pain management,27 repositioning during labor,71 continuous labor support,72 and oral intake during labor.73

Additionally, communication and decision-making may play a role in the use of interventions and cesarean birth. However, these variables are not routinely recorded in the electronic medical record and require future research involving a prospective design.

A third limitation is that an examination of the timing and sequence of interventions was not feasible due to large amounts of missing data for these variables. It should be noted that the cesarean birth rate in this study of 13.7% was lower than the overall NTSV cesarean birth rate of 23.9% in the Consortium on Safe Labor for all types

60 of admission (e.g., spontaneous onset of labor, induction of labor, pre-labor cesarean).

One explanation is that the low cesarean birth rate in this study is due to the exclusion of women who underwent induction of labor. Therefore, future research should include an analysis of the timing and sequence of interventions that includes a comparison between women with spontaneous onset of labor versus those undergoing induction of labor.

Conclusion

Findings from this study show that likelihood of cesarean birth varies depending on whether intrapartum interventions are applied individually or in combination. Despite the limitations of this study, these results contribute to the knowledge about how practice patterns influence the use of cesarean birth. Future research is needed to examine the effect of timing and sequence of intrapartum interventions on cesarean birth.

Chapter 5: Discussion

Chapters two, three, and four were completed as manuscripts that address the three specific aims of this dissertation. This final chapter provides a summary of findings as well as a discussion of strengths and limitations, implications for policy and practice, and recommendations for future research.

5.1 SUMMARY OF FINDINGS

Overall, there was strong evidence to accept the alternative hypothesis. Results showed that regardless of the total number of interventions applied (1, 2, or 3) a greater percentage of women admitted prior to 3 cm dilation received labor management interventions compared to women admitted at 4-5 cm or 6-10 cm dilation. Women were

55% less likely to receive the combination of amniotomy, epidural, and oxytocin when admitted at 6-10 cm (RR 0.40, CI95 0.35-0.46) compared to those admitted at 0-3 cm.

Likelihood of cesarean birth was lower for women admitted at 4-5 cm (RR 0.44, CI95

0.40-0.49) and 6-10 cm dilation (RR 0.20, CI95 0.17-0.24) compared to those admitted at

0-3 cm dilation. Despite that existing research has used varying benchmarks to distinguish early labor from active labor, the results from this dissertation are consistent

62 with findings showing a lower likelihood of cesarean delivery associated with admission at more advanced dilation.32–36

Providers had a greater variation in cesarean rates (1% to 80%) compared to the variation among eight hospitals included in the study (8.8% to 19.5%). MFM specialists had a higher cesarean birth rate compared to non-MFM specialists and family practice physicians had a lower cesarean birth rate compared to non-family practice physicians.

There was strong evidence to accept the alternative hypothesis that a physician provider independently predicts the likelihood of interventions used individually and in combination. Compared to obstetrician/gynecologist (OB/GYN) physicians, midwives were nearly twice as likely to use no intrapartum interventions (RR 1.81, CI95 1.50-2.19) and were 23% less likely to use amniotomy-epidural-oxytocin (RR 0.77, CI95 0.66-0.91).

Additional results showed that female providers had a 22% higher likelihood of using no intrapartum interventions (RR 1.22, CI95 1.05-1.41) and were half as likely to perform cesarean deliveries (RR 0.5, CI95 0.42-0.61). Family practice physicians also had a lower likelihood of using amniotomy-epidural-oxytocin (RR 0.82, CI95 0.70-0.95) and

63 performing cesarean deliveries (RR 0.45, CI95 0.34-0.58) compared to obstetrician/gynecologists.

There was strong evidence to accept the alternative hypothesis that availability of a 24/7 laborist independently predicts the likelihood of interventions used individually and in combination. Compared to having a laborist available 24/7, an as-needed laborist was associated with a four times higher likelihood of no interventions (RR 4.27, CI95

1.43-12.70). Hospital type was the only characteristic that was significantly associated with likelihood of cesarean birth, where women delivering at a community teaching hospital had a 31% lower likelihood of cesarean birth compared to women delivering at a university teaching hospital (RR 0.69, CI95 0.68-0.70).

There was strong evidence to accept the alternative hypothesis. Compared with women who received no interventions, those receiving amniotomy only (RR 1.59, CI95

1.28-1.98) and oxytocin only (RR 1.64, CI95 1.22-2.21) had a significantly increased likelihood of cesarean birth. Likelihood of cesarean birth increased when amniotomy and oxytocin were paired with additional interventions. Women who received all three interventions had nearly twice the likelihood of cesarean birth compared to those who received no interventions (RR 1.84, CI95 1.53-2.21).

5.2 STRENGTHS, LIMITATIONS, AND RECOMMENDATIONS

The strengths of this dissertation are large sample sizes and the inclusion of eight or more hospitals for each aim. Additionally, this dissertation examined clinical-level processes involved in the management of labor. Detailed clinical information about labor management is only available in the electronic medical record, thus presenting a challenge to researchers interested in exploring variation in practice patterns across institutions. Much of the existing maternity care research in the United States relies on

ICD-9 codes, birth certificate data, and discharge abstract data like the Healthcare Cost and Utilization Project (HCUP). Therefore, the exploration of electronic medical record data in this dissertation, particularly in relation to provider and hospital characteristics, contributes new knowledge about labor management in the United States.

Another strength of this dissertation is the focus on women who are low-risk for cesarean birth, defined as nulliparous and pregnant with a term, singleton gestation in the vertex position (NTSV). Several possible risk factors for cesarean birth were eliminated by narrowing the CSL dataset to include only NTSV women. Additionally, the NTSV cesarean birth rate is widely recognized as an indicator of maternity care quality and is tracked through a Healthy People 2020 Objective and a National Quality Forum-endorsed measure used by the Joint Commission.94–96 By focusing on NTSV women, results from this dissertation will contribute to the knowledge about how to prevent cesarean birth in this low-risk group. A consideration for future research is that the target cesarean birth rate for NTSV may need to be revised based on the low-risk nature of this group. A 10-

19% cesarean birth rate is considered to be the threshold below which maternal and neonatal mortality do not decline.13,14 However, these rates are based on international

65 studies that did not specifically focus on NTSV women. Therefore, the 10-19% threshold may not be an appropriate goal for NTSV women because they lack many of the risk factors associated with a history of prior cesarean birth, including placental complications and risk of uterine rupture.62 Research is needed to determine the cesarean birth rate associated with optimal maternal and neonatal outcomes for NTSV women.

Several limitations of this dissertation must be acknowledged. First, births from the Consortium on Safe Labor dataset occurred from 2002-2008. It should be noted that

87% of births in the dataset occurred from 2005-2007,97 and a similarly high prevalence occurred during these years for each aim in this dissertation. Although no major changes in practice have been documented in the literature since 2005, there have been two noteworthy practice publications. First, the American College of Obstetricians and

Gynecologists (ACOG) and the Society for Maternal Fetal Medicine published a joint commission consensus statement in 2014 on strategies to prevent primary cesarean birth.3

This statement noted that active labor does not begin until 6 cm of cervical dilation, possibly leading to modified admission practices since 2014. Additionally, cesarean birth should only be performed for arrest of active labor in the event of inadequate uterine activity or cervical change following six hours of oxytocin administration. The latter recommendation suggests that women experiencing arrest of active labor will be more likely to receive oxytocin augmentation to manage labor after the 2014 publication of this consensus statement. ACOG also published a committee opinion in 2017 outlining strategies to limit the use of interventions during labor and birth.92 A few recommendations in this committee opinion are relevant to the analyses in this dissertation. First, expectant management is recommended for women who are in latent

66 labor (<4-6 cm cervical dilation) and whose maternal and fetal status are reassuring.

Second, routine amniotomy is discouraged in women whose labor is progressing normally with no evidence of fetal compromise. Third, ACOG recommends consideration of non-pharmacologic pain management techniques as an option in addition to the availability of epidural anesthesia upon request. Although these practice guidelines are a step toward standardization of labor management practices, more research is needed to inform the timing of interventions as well as the use of multiple interventions in combination.

A second limitation of this dissertation is the use of a convenience sample of hospitals. The parent dataset included a weighted variable that accounted for hospital statistics from the American Hospital Association and national birth certificate data from the National Center for Health Statistics to better reflect the contemporary population in the United States. However, it is noteworthy that the dataset does not include hospitals located in rural areas. Therefore, results are limited to hospital settings located in more urban areas of the United States. Additionally, the cesarean birth rate varies in the CSL dataset depending on onset of labor. The NTSV cesarean birth rate for all hospitals included in the CSL dataset was 23.9%. This rate is similar to the national rate of 26% for

NTSV cesarean birth in 2014.59 In contrast, the CSL cesarean birth rate for NTSV women with spontaneous onset of labor (versus induction of labor or pre-labor cesarean birth) was 14.7%. Although literature examining the relationship between induction of labor and cesarean birth shows mixed results, induction of labor is likely associated with a greater use of labor management interventions. Upon admission to the hospital setting, induction requires a minimum of several procedures including medication administration

67 or device application, possible intravenous line insertion and fluid infusion, and continuous electronic fetal monitoring.98 Comparing the timing and sequence of interventions for women admitted with spontaneous onset of labor versus those undergoing induction of labor may provide some insight about the relationship between induction of labor and cesarean birth.

Another limitation was that large amounts of data were missing for particular variables in the CSL dataset. In particular, some hospitals had completely missing data for key variables of interest. This limitation is acknowledged in the CSL dataset documentation and the recommendation is to exclude hospitals from the analysis in cases where data is completely missing by hospital for a key variable. As a result, the sample sizes and number of hospitals varied slightly, ranging from seven to 11 hospitals and from n=17,443 to n=26,259 deliveries for each aim of this dissertation. Sample characteristics were compared across aims and against NTSV women with spontaneous onset of labor from all 19 hospitals (data not shown). The sample that included all 19 hospitals had a higher proportion of Black/Non-Hispanic women (21.7% versus 6.5%-

13.1% across aims) as well as a higher proportion of single women (53.2% versus 31.6%-

38.9% across aims). The sample that included all hospitals also a higher proportion of births that were attended by a physician/midwife team (14.9% versus 2.4%-5.5% across aims). Frequency of intervention use was also compared against published data that reporting the use of epidural anesthesia (60%) and oxytocin augmentation (37%) for nulliparous women with spontaneous onset of labor across all 19 hospitals of the CSL dataset (n=43,576).99 In comparison, the use of epidural anesthesia in each sample

68 examined in this dissertation ranged from 79.9% to 82.1% and the use of oxytocin augmentation ranged from 44.1% to 49.6%.

An additional limitation was the inability to examine timing and sequence of interventions due to large amounts of missing data for these variables. Therefore, it was not possible to determine whether the order in which interventions were applied would affect likelihood of cesarean birth. For example, our results show that the combined application of amniotomy-epidural-oxytocin is associated with increased likelihood of cesarean birth, but perhaps likelihood of cesarean birth varies depending on the order in which interventions were applied. Some research has shown that epidural anesthesia may interfere with release of oxytocin, resulting in slowed labor progression.29 Thus, application of epidural anesthesia as the first intervention may lead to the use of amniotomy and oxytocin to augment labor. Another possibility may occur for women who exhibit a slow or dysfunctional labor pattern, possibly due to admission in latent labor. In this scenario, women may receive amniotomy and/or oxytocin as the first intervention to augment labor. Increased pain associated with augmentation of labor may lead to use of epidural anesthesia followed by augmentation via additional augmentation with amniotomy or oxytocin infusion in cases where these interventions have not already been applied. Future research with a longitudinal design is needed to examine the association between sequence and timing of interventions and cesarean birth.

An additional limitation of using existing data from electronic medical records was that only a few labor management interventions were included in this dissertation.

This is because many interventions used to manage labor are not routinely recorded in the electronic medical record. These include interventions shown to reduce cesarean birth

69 such as non-pharmacological pain management,27 repositioning during labor,71 continuous labor support,72 and oral intake during labor.73 Interventions such as continuous intravenous infusion and continuous electronic fetal monitoring may increase risk of cesarean birth by restricting mobility. These interventions were not included in the

Consortium on Safe Labor dataset, but it is believed that continuous intravenous infusion and continuous electronic fetal monitoring are nearly universally applied during labor in the hospital setting in the United States. Therefore, it is likely that data from deliveries that occur in the hospital setting would not include enough variation in the use of intravenous infusion and continuous electronic fetal monitoring to allow a comparison with women not receiving these interventions. Future research with a prospective design is needed to examine the use of interventions that are not routinely recorded in the electronic medical record. Examining the use of interventions that are universally applied in the hospital setting presents an additional challenge. Research examining the influence of continuous intravenous infusion and electronic fetal monitoring would require matched cohorts, likely from a hospital setting and a birth center setting where these interventions are not routinely applied. However, this approach presents an additional challenge of controlling for differences between a hospital setting and a birth center setting.

5.3 POLICY AND PRACTICE IMPLICATIONS

Reducing unnecessary variation in cesarean birth among NTSV women is key to improving the quality of maternity care in the United States. The National Quality Forum has endorsed measure #0471 PC-02 Cesarean Section to assess the number of NTSV women who have a cesarean birth. This measure is used by The Joint Commission and

The Centers for Medicare and Medicaid Services among other organizations to assess the

70 quality of maternity care in the Unites States. Additional quality measures are needed to measure processes that are associated with a lower likelihood of NTSV cesarean birth.

For example, a quality measure to assess the number of NTSV women admitted prior to the onset of active labor is justified by mounting evidence that admission to the hospital in early labor is associated with increased likelihood of cesarean birth. Additionally, a quality measure assessing the number of NTSV women who receive no labor management interventions would provide information about the use of interventions in the hospital setting. This could provide critical information to reduce variation in NTSV cesarean birth rates based on results of this dissertation showing that the use of no interventions is associated with a lower likelihood of cesarean birth.

Current guidelines for the use of labor management interventions do not address the use of multiple interventions over the course of labor. Despite that the majority of women in the United States receive multiple labor management interventions,68 existing guidelines address the use of interventions as isolated practices. For example, a recent recommendation from the ACOG discourages the routine use of continuous intravenous infusion and amniotomy in women with normally progressing labor.92 Another recommendation from the ACOG states that women should be given epidural anesthesia upon request.100 The ACOG position on augmentation with oxytocin provides only vague guidance, stating that the dose should be titrated based on dose response.101 Another shortcoming of current recommendations is that guidelines are not written specifically for the management of low-risk NTSV women. More research is needed to inform guidelines that would standardize the use of interventions such as epidural anesthesia and oxytocin augmentation, as well as the combined use of interventions in low-risk women.

5.4 CONCLUSION

This dissertation contributes findings to better understand factors that influence the use of labor management interventions and their effect on cesarean birth. Some factors that are associated with the use of labor management interventions and cesarean birth, such as provider sex, are non-modifiable; However, many factors associated with cesarean birth are modifiable. For example, admission to the hospital can be delayed until the onset of active labor through patient education and shared decision-making between women and providers. Provider education and training could also be modified to encourage the use of labor management interventions associated with reduced cesarean birth. Results from this dissertation show that the association between labor management interventions and cesarean birth vary depending on whether interventions are used alone or in combination. Future research is needed to gain a greater understanding of how the timing and sequence of labor management interventions influences cesarean birth.

References

1. Placek PJ, Taffel SM. Trends in cesarean section rates for the United States, 1970- 78. Public Health Rep. 1970;95(6):540-548. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1422801&tool=pmcen trez&rendertype=abstract.

2. Martin JA, Hamilton BE, Osterman MJ. NCHS Data Brief: Births in the United States, 2016. 2017. https://www.cdc.gov/nchs/data/databriefs/db287.pdf. 3. Caughey AB, Cahill AG, Guise J-M, Rouse DJ. Safe prevention of the primary cesarean delivery. Am J Obstet Gynecol. 2014;210(3):179-193. doi:10.1016/j.ajog.2014.01.026.

4. Moraitis AA, Oliver-Williams C, Wood AM, Fleming M, Pell JP, Smith GCS. Previous caesarean delivery and the risk of unexplained stillbirth: Retrospective cohort study and meta-analysis. BJOG An Int J Obstet Gynaecol. 2015;122(11):1467-1474. doi:10.1111/1471-0528.13461.

5. Blondon M, Casini A, Hoppe KK, Boehlen F, Righini M, Smith NL. Risks of venous thromboembolism after cesarean sections: A meta-analysis. Chest. 2016;150(3):572-596. doi:10.1016/j.chest.2016.05.021.

6. Rossi AC, Addario V. Maternal morbidity following a trial of labor after cesarean section vs elective repeat cesarean delivery: a systematic review with metaanalysis. Am J Obstet Gynecol. 2008;199(3):224-231. doi:10.1016/j.ajog.2008.04.025.

7. Curtin SC, Gregory KD, Korst LM, Uddin SF. Maternal morbidity for vaginal and cesarean deliveries, according to previous cesarean history: New data From the birth certificate, 2013. Natl Vital Stat Reports. 2015;64(4).

8. Thavagnanam S, Fleming J, Bromley A, Shields MD, Cardwell CR. A meta- analysis of the association between caesarean section and childhood asthma. Clin Exp Allergy. 2008;38(4):629-633. doi:10.1111/j.1365-2222.2007.02780.x.

9. Magnus MC, Håberg SE, Stigum H, et al. Delivery by cesarean section and early childhood respiratory symptoms and disorders: the Norwegian mother and child cohort study. Am J Epidemiol. 2011;174(11):1275-1285. doi:10.1093/aje/kwr242. 10. Kamath BD, Todd JK, Lezotte D. Neonatal outcomes after elective cesarean delivery. Obstet Gynecol. 2009;113(6):1231-1238.

11. Kuhle S, Tong OS, Woolcott CG. Association between caesarean section and childhood obesity: A systematic review and meta-analysis. Obes Rev. 2015;16(4):295-303. doi:10.1111/obr.12267.

12. Cardwell CR, Stene LC, Joner G, et al. Caesarean section is associated with an

increased risk of childhood-onset type 1 diabetes mellitus: A meta-analysis of observational studies. Diabetologia. 2008;51(5):726-735. doi:10.1007/s00125- 008-0941-z.

13. Ye J, Betrán AP ila., Guerrero Vela M, Souza JP, Zhang J. Searching for the optimal rate of medically necessary cesarean delivery. Birth. 2014;41(3):237-244. doi:10.1111/birt.12104.

14. Molina G, Weiser TG, Lipsitz SR, et al. Relationship between cesarean delivery rate and maternal and neonatal mortality. JAMA - J Am Med Assoc. 2015;314(21):2263-2270. doi:10.1001/jama.2015.15553.

15. Centers for Disease Control and Prevention. Cesarean Delivery Rate by State. National Center for Healthcare Statistics. https://www.cdc.gov/nchs/pressroom/sosmap/cesarean_births/cesareans.htm. Published 2018. Accessed March 3, 2018.

16. Kozhimannil KB, Law MR, Virnig BA. Cesarean delivery rates vary tenfold among US hospitals; Reducing variation may address quality and cost issues. Health Aff. 2013;32:527-535. doi:10.1377/hlthaff.2012.1030.

17. Barber EL, Lundsberg LS, Belanger K, Pettker CM, Funai EF, Illuzzi JL. Indications contributing to the increasing cesarean delivery rate. Obstet Gynecol. 2011;118(1):29-38. doi:10.1097/AOG.0b013e31821e5f65.

18. Marshall NE, Fu R, Guise JM. Impact of multiple cesarean deliveries on maternal morbidity: A systematic review. Am J Obstet Gynecol. 2011;205(3). doi:10.1016/j.ajog.2011.06.035.

19. Silver RM. Implications of the first cesarean: perinatal and future reproductive health and subsequent cesareans, placentation issues, uterine rupture risk, morbidity, and mortality. Semin Perinatol. 2012;36(5):315-323. doi:10.1053/j.semperi.2012.04.013.

20. Poobalan AS, Aucott LS, Gurung T, Smith WC, Bhattacharya S. Obesity as an independent risk factor for elective and emergency caesarean delivery in nulliparous women--systematic review and meta-analysis of cohort studies. Obes Rev. 2009;10(1):28-35. doi:10.1111/j.1467-789X.2008.00537.x.

21. Bayrampour H, Heaman M. Advanced maternal age and the risk of cesarean birth: a systematic review. Birth. 2010;37(3):219-226. doi:10.1111/j.1523- 536X.2010.00409.x.

22. Boyle A, Reddy UM. Epidemiology of Cesarean Delivery: The Scope of the Problem. Semin Perinatol. 2012;36(5):308-314. doi:10.1053/j.semperi.2012.04.012.

23. Getahun D, Strickland D, Lawrence JM, Fassett MJ, Koebnick C, Jacobsen SJ. Racial and ethnic disparities in the trends in primary cesarean delivery based on indications. Am J Obstet Gynecol. 2009;201(4):422.e1-422.e7. doi:10.1016/j.ajog.2009.07.062.

24. Coonrod D V., Drachman D, Hobson P, Manriquez M. Nulliparous term singleton vertex cesarean delivery rates: institutional and individual level predictors. Am J Obstet Gynecol. 2008;198(6). doi:10.1016/j.ajog.2008.03.026.

25. Declercq E, Menacker F, Macdorman M. Maternal risk profiles and the primary cesarean rate in the United States, 1991-2002. Am J Public Health. 2006;96(5):867-872. doi:10.2105/AJPH.2004.052381.

26. Brody H, Sakala C. Revisiting “the maximin strategy in modern obstetrics.” J Clin Ethics. 2013;24(3):198-206.

27. Rossignol M, Chaillet N, Boughrassa F, Moutquin JM. Interrelations between four antepartum obstetric interventions and cesarean delivery in women at low risk: A systematic review and modeling of the cascade of interventions. Birth. 2014;41(March):70-78. doi:10.1111/birt.12088.

28. Shilling T. Healthy Birth Practices #2: Walk, Move Around, and Change Positions Throughout Labor. J Perinat Educ. 2009;23(4):3.

29. Buckley SJ. Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care. Childbirth Connect Programs, Natl Partnersh Women Fam. 2015.

30. Petersen A, Poetter U, Michelsen C, Gross MM. The sequence of intrapartum interventions: a descriptive approach to the cascade of interventions. Arch Gynecol Obstet. 2013;288:245-254. doi:10.1007/s00404-013-2737-8.

31. Tracy SK, Sullivan E, Wang YA, Black D, Tracy M. Birth outcomes associated with interventions in labour amongst low risk women: A population-based study. Women and Birth. 2007;20(2):41-48. doi:10.1016/j.wombi.2007.03.005.

32. Mikolajczyk R, Zhang J, Chan L, Jagteshwar G. Early versus late admission to labor/delivery, labor progress, and risk of cesarean section in nulliparous women. Am J Obstet Gynecol. 2008;199(6):S49. doi:10.1016/j.ajog.2008.09.155.

33. Neal JL, Lamp JM, Buck JS, Lowe NK, Gillespie SL, Ryan SL. Outcomes of nulliparous women with spontaneous labor onset admitted to hospitals in preactive versus active labor. J Midwifery Women’s Heal. 2014;59(1):28-34. doi:10.1111/jmwh.12160.

34. Davey MA, McLachlan HL, Forster D, Flood M. Influence of timing of admission in labour and management of labour on method of birth: Results from a randomised controlled trial of caseload midwifery (COSMOS trial). Midwifery. 2013;29(12):1297-1302. doi:10.1016/j.midw.2013.05.014.

35. Rahnama P, Ziaei S, Faghihzadeh S. Impact of early admission in labor on method of delivery. Int J Gynecol Obstet. 2006;92(3):217-220. doi:10.1016/j.ijgo.2005.12.016.

36. Kauffman E, Souter V, Katon J, Sitcov K. Cervical dilation on admission in term spontaneous labor and maternal and newborn outcomes. Obstet Gynecol. 2016;127(3):481-488. doi:10.1097/AOG.0000000000001294.

37. Declercq ER, Sakala C, Corry MP, Applebaum S. Listening to Mothers II: Report of the Second National U.S. Survey of Women’s Childbearing Experiences: Conducted January-February 2006 for Childbirth Connection by Harris Interactive(R) in partnership with Lamaze International. J Perinat Educ. 2007;16(4):9-14. doi:10.1624/105812407X244769.

38. Martin JA, Hamilton BE, Osterman MJKS, Driscoll AK, Drake P. Births: Final Data for 2016. Natl Vital Stat Reports. 2018;67(1). https://www.cdc.gov/nchs/data/nvsr/nvsr67/nvsr67_01.pdf.

39. Zhang J, Landy HJ, Branch DW, et al. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol. 2010;116(6):1281-1287. doi:10.1097/OGX.0b013e31821685d0.

40. Nijagal MA, Kuppermann M, Nakagawa S. Two practice models in one labor and delivery unit : association with cesarean. Am J Obstet Gynecol. 2015;212(4):491.e1-491.e8. doi:10.1016/j.ajog.2014.11.014.

41. Iriye BK, Huang WH, Condon J, et al. Implementation of a laborist program and evaluation of the effect upon cesarean delivery. Am J Obstet Gynecol. 2013;209(3):251.e1-251.e6. doi:10.1016/j.ajog.2013.06.040.

42. Janssen PA, Klein MC, Soolsma JH. Differences in institutional cesarean delivery rates-the role of pain management. J Fam Pract. 2001;50(3):217-223.

43. Haberman S, Saraf S, Zhang J, et al. Nonclinical parameters affecting primary cesarean rates in the united states. Am J Perinatol. 2014;31(3):213-221. doi:10.1055/s-0033-1345263.

44. Sandall J, Soltani H, Gates S, et al. Midwife-led continuity models versus other models of care for childbearing women (Review). Cochrane Collab. 2016;(9):10- 13. doi:10.1002/14651858.CD004667.pub4.Copyright.

45. Mitler LK, Rizzo JA, Horwitz SM. Physician gender and cesarean sections. J Clin Epidemiol. 2000;53(10):1030-1035. doi:10.1016/S0895-4356(00)00221-3.

46. Johantgen M, Fountain L, Zangaro G, Newhouse R, Stanik-Hutt J, White K. Comparison of labor and delivery care provided by certified nurse-midwives and physicians: A systematic review, 1990 to 2008. Women’s Heal Issues. 2012;22(1):e73-e81. doi:10.1016/j.whi.2011.06.005.

47. Sandall J, Soltani H, Gates S, et al. Midwife-led continuity models versus other models of care for childbearing women (Review). Cochrane Database Syst Rev. 2013;(8). doi:10.1002/14651858.CD004667.pub3.Copyright.

48. Smyth R, Alldred SK, Markham C. Amniotomy for shortening spontaneous labour. Cochrane Database Syst Rev. 2013;(4). doi:10.1002/14651858.CD006167.

49. Wei S, Wo BL, Xu H, Luo ZC, Roy C, Fraser WD. Early amniotomy and early oxytocin for prevention of, or therapy for, delay in first stage spontaneous labour compared with routine care. Cochrane Database Syst Rev. 2013;(2). doi:10.1002/14651858.CD006794.pub2.

50. Anim-Somuah M, Smyth R, Jones L. Epidural versus non-epidural or no analgesia in labour (Review). Cochrane Database Syst Rev. 2011;(12). doi:10.1002/14651858.CD000331.pub2.

51. Costley PL, East CE. Oxytocin augmentation of labour in women with epidural analgesia for reducing operative deliveries. Cochrane Database Syst Rev. 2013;(7). doi:10.1002/14651858.CD009241.pub3.

52. Petersen A, Ayerle GM, Frömke C, Hecker H, Gross MM. The timing of interventions during labour: Descriptive results of a longitudinal study. Midwifery. 2011;27(6):267-273. doi:10.1016/j.midw.2010.10.017.

53. Petersen A, Poetter U, Michelsen C, Gross MM. The sequence of intrapartum interventions: A descriptive approach to the cascade of interventions. Arch Gynecol Obstet. 2013;288(2):245-254. doi:10.1007/s00404-013-2737-8.

54. Gross MM, Frömke C, Hecker H. The timing of amniotomy, oxytocin and neuraxial analgesia and its association with labour duration and mode of birth. Arch Gynecol Obstet. 2014;289(1):41-48. doi:10.1007/s00404-013-2916-7.

55. Martin JA, Hamilton BE, Osterman MJK, Curtin SC, Mathews TJ. National Vital Statistics Reports Births: Final Data for 2015. Natl Vital Stat Reports. 2017;66(1).

56. Baker D.P., Gustafson S., Beaubien J.M., Salas E. BP. Medical Teamwork and Patient Safety: The Evidence-Based Relation Literature Review.; 2005.

57. Coyle YM, Battles JB. Using antecedents of medical care to develop valid quality of care measures. Int J Qual Heal Care. 1999;11(1):5-12. doi:10.1093/intqhc/11.1.5.

58. Donabedian A. Evaluating the quality of medical care. Milibank Meml Fund Q. 1966;44(3):166-203.

59. Osterman MJK, Martin JA. Trends in low-risk cesarean delivery in the United States, 1990–2013. Natl Vital Stat Reports. 2014;63(6).

60. Liu S, Liston RM, Joseph KS, Heaman M, Sauve R, Kramer MS. Maternal mortality and severe morbidity associated with low-risk planned cesarean delivery versus planned vaginal delivery at term. Can Med Assoc. 2007;176(4):455-460.

61. Shellhaas CS, Gilbert S, Landon MB, et al. The frequency and complication rates of hysterectomy accompanying cesarean delivery. Obstet Gynecol. 2009;114(2):224-229. doi:10.1097/AOG.0b013e3181ad9442.

62. Silver RM, Landon MB, Rouse DJ, et al. Maternal Morbidity Associated With Multiple Repeat Cesarean Deliveries. Obstet Gynecol. 2006;107(6):1226-1232.

63. Gibbons L, Belizán JM, Lauer J a, Betrán AP, Merialdi M, Althabe F. The Global Numbers and Costs of Additionally Needed and Unnecessary Caesarean Sections Performed per Year: Overuse as a Barrier to Universal Coverage. World Heal Rep Backgr Pap. 2010:1-31.

64. Neal JL, Lowe NK, Ahijevych KL, Patrick TE, Cabbage LA, Corwin EJ. “Active labor” duration and dilation rates among low-risk, nulliparous women with spontaneous labor onset: a systematic review. J Midwifery Womens Health. 2010;55(4):308-318. doi:10.1016/j.jmwh.2009.08.004.

65. Sakala C, Romano AM, Buckley SJ. Hormonal Physiology of Childbearing, an Essential Framework for Maternal–Newborn Nursing. J Obstet Gynecol Neonatal Nurs. 2016;45(2):264-275. doi:10.1016/j.jogn.2015.12.006.

66. Bailit JL, Dierker L, Blanchard MH, Mercer BM. Outcomes of women presenting in active versus latent phase of spontaneous labor. Obstet Gynecol. 2005;105(1):77-79. doi:10.1097/01.AOG.0000147843.12196.00.

67. Rossignol M, Chaillet N, Boughrassa F, Moutquin JM. Interrelations between four antepartum obstetric interventions and cesarean delivery in women at low risk: A systematic review and modeling of the cascade of interventions. Birth. 2014;41(1):70-78. doi:10.1111/birt.12088.

68. Declercq ER, Sakala C, Corry MP, Applebaum S, Herrlich A. Major Survey Findings of Listening to Mothers III: New Mothers Speak Out. J Perinat Educ.

2013;23(1):17-24. 69. Chuma C, Kihunrwa A, Matovelo D, Mahendeka M. Labour management and Obstetric outcomes among pregnant women admitted in latent phase compared to active phase of labour at Bugando Medical Centre in Tanzania. BMC Pregnancy Childbirth. 2014;14(1):68. doi:10.1186/1471-2393-14-68.

70. Kulie T, Slattengren A, Redmer J, Counts H, Eglash A, Schrager S. Obesity and women’s health: An evidence-based review. J Am Board Fam Med. 2011;24(1):75-85. doi:10.3122/jabfm.2011.01.100076.

71. Lawrence A, Lewis L, Hofmeyr G, Styles C. Maternal positions and mobility during first stage labour (Cochrane Review). Cochrane Database Syst Rev. 2013;(10). doi:10.1002/14651858.CD003934.pub4.www.cochranelibrary.com.

72. Hodnett E, Gates S, Hofmeyr G, Sakala C. Continuous Support for women during chidlbirth. Cochrane Database Syst Rev. 2013;(7). doi:10.1002/14651858.CD003766.pub3.

73. Shea-Lewis A, Eckardt P, Stapleton D. An Investigation into the Safety of Oral Intake During Labor. Am J Nurs. 2007;118(3):24-31.

74. Martin JA, Hamilton BE, Osterman MJK, Curtin SC, Matthews TJ. National Vital Statistics Report Births: Final Data for 2012.; 2013. http://www.cdc.gov/nchs/data/nvsr/nvsr62/nvsr62_09.pdf. Accessed September 9, 2014.

75. DeMott RK, Sandmire HF. The Green Bay cesarean section study: The physician factor as a determinant of cesarean birth rates. Am J Obstet Gynecol. 1990;162(6):1593-1599.

76. Goyert GL, Bottoms SF, Treadwell MC, Nehra PC. The physician factor in cesarean birth rates. N Engl J Med. 1989;320(11):706-709.

77. Segal S, Blatman R, Dobie M, Datta S. The Influence of the Obstetrician in the Relationship between Epidural Analgesia and Cesarean Section for Dystocia. Anesthesiology. 1999;91:90-96.

78. Goyert G., Bottoms SF, Treadwell M, Nehra PC. The Physician Factor in Cesarean Birth Rate. 1New Engl J Med. 1989;320(11):706-709.

79. Edmonds JK, O’Hara M, Clarke SP, Shah NT. Variation in Cesarean Birth Rates by Labor and Delivery Nurses. JOGNN - J Obstet Gynecol Neonatal Nurs. 2017;46(4):486-493. doi:10.1016/j.jogn.2017.03.009.

80. Janssen PA, Klein MC, Soolsma JH. Differences in institutional cesarean delivery rates-the role of pain management. J Fam Pract. 2001;50(3):217-223.

http://www.ncbi.nlm.nih.gov/pubmed/11252209.

81. Iriye BK, Huang WH, Condon J, et al. Implementation of a laborist program and evaluation of the effect upon cesarean delivery. Am J Obstet Gynecol. 2013;209(3):251.e1-251.e6. doi:10.1016/j.ajog.2013.06.040.

82. Luthy DA, Malmgren JA, Zingheim RW, Leininger CJ. Physician contribution to a cesarean delivery risk model. Am J Obstet Gynecol. 2003;188(6):1579-1587. doi:10.1067/mob.2003.389.

83. Pasko DN. The impact of patient, provider, and hospital characteristics on variation in the NTSV cesarean rate. Am J Obstet Gynecol. 2017;216(1 Supplement 1):S41-S42. doi:10.1016/j.ajog.2016.11.943.

84. Sebastiao YV, Womack L, Vamos CA, et al. Hospital variation in cesarean delivery rates: contribution of individual and hospital factors in Florida. Am J Obstet Gynecol. 2016;214(123):e1-18. doi:10.1016/j.ajog.2015.08.027.

85. Main EK, Moore D, Farrell B, et al. Is there a useful cesarean birth measure? Assessment of the nulliparous term singleton vertex cesarean birth rate as a tool for obstetric quality improvement. Am J Obstet Gynecol. 2006;194(6):1644-51-2. doi:10.1016/j.ajog.2006.03.013.

86. U.S. Department of Health and Human Services. Healthy People 2020 Leading Health Indicators: Maternal, Infant, and Child Health.; 2014. http://www.healthypeople.gov/sites/default/files/HP2020_LHI_Mat_Inf_Child.pdf.

87. Kozhimannil KB, Arcaya MC, Subramanian S V. Maternal Clinical Diagnoses and Hospital Variation in the Risk of Cesarean Delivery : Analyses of a National US Hospital Discharge Database. 2014;11(10). doi:10.1371/journal.pmed.1001745.

88. Clark SL, Belfort MA, Hankins GD V, Meyers JA, Houser FM. Variation in the rates of operative delivery in the United States. Am J Obstet Gynecol. 2007;196:536.e1-526.e5. doi:10.1016/j.ajog.2007.01.024.

89. Buckles KS, Chandra A. Geographic Variation In The Appropriate Use Of Cesarean Delivery. Health Aff. 2006;25(5):w355-367.

90. Bugg GJ, Siddiqui F, Thornton JG. Oxytocin versus placebo or no treatment for slow progress in the first stage of spontaneous labour. Cochrane Database Syst Rev. 2008;(2). doi:10.1002/14651858.CD007123.

91. ACOG. Obstetric Analgesia and Anesthesia - ACOG Practice Bulletin. Obstet Gynecol. 2017;129(4):766-768. http://www.acog.org/Resources-And- Publications/Practice-Bulletins/Committee-on-Practice-Bulletins- Obstetrics/Obstetric-Analgesia-and-Anesthesia.

92. ACOG. Approaches to Limit Intervention During Labor and Birth Committee on Obstetric Practice. Am Coll Obstet Gynecol. 2017;687. doi:10.1097/AOG.0000000000001905.

93. Declercq ER, Sakala C, Corry MP, Applebaum S, Herrlich A. Listening to Mothers III: New Mothers Speak Out.; 2013. http://transform.childbirthconnection.org/wp-content/uploads/2013/06/LTM- III_NMSO.pdf.

94. Agency for Healthcare Research and Quality. Measure Fact Sheet – The AHRQ- CMS Pediatric Quality Measures Program (PQMP). Measure:Cesarean Delivery for Nulliparous (NTSV) Women (Appropriate Use). https://www.ahrq.gov/sites/default/files/wysiwyg/policymakers/chipra/factsheets/c hipra_1415-p009-5-ef.pdf. Published 2015.

95. The Joint Commission. Explanation for PC-02: Cesarean Birth. https://www.jointcommission.org/assets/1/6/PC- 02_Cesarean_Birth_Explanation.pdf. Published 2015.

96. U.S. Department of Health and Human Services. Healthypeople.gov. Maternal, Infant, and Child Health.

97. Zhang J, Troendle J, Reddy UM, et al. Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol. 2010;203(4):326.e1-326.e10. doi:10.1016/j.ajog.2010.06.058.

98. Insitute for Safe Medication Practices. ISMP List of High-Alert Medications in Acute Care Settings.; 2014. https://www.ismp.org/tools/institutionalhighAlert.asp. 99. Laughon SK, Branch DW, Beaver J, Zhang J. Changes in labor patterns over 50 years. Am J Obstet Gynecol. 2012;206(5):419.e1-9. doi:10.1016/j.ajog.2012.03.003.

100. ACOG. Obstetric Analgesia and Anesthesia - ACOG Practice Bulletin. Obstet Gynecol. 2017;129(4):766-768.

101. ACOG. Dystocia and augmentation of labor. Obstet Gynecol. 2003;102(1):203- 213. doi:10.1016/S0029-7844(03)00610-0.