Vaginal Birth After Cesarean Success in High-Risk Women: a Population-Based Study

ORIGINAL ARTICLE Vaginal birth after cesarean success in high-risk women: a population-based study

J Regan1, C Keup1, K Wolfe1, C Snyder1 and E DeFranco1,2

OBJECTIVE: The study aim was to identify factors associated with vaginal birth after cesarean (VBAC) in high-risk women. STUDY DESIGN: This is a population-based retrospective cohort study of all births in Ohio during 2006 and 2007. High-risk patients were defined as singleton gestations in women with one previous cesarean who had ⩾ 1 of the following risk factors: body mass index (BMI) ⩾ 30, hypertension, or diabetes. Multivariate logistic regression was utilized to estimate the relative influence of each factor on successful VBAC. RESULT: A total of 280 882 births were analyzed: of them, 79 084 (27.1%) were high-risk pregnancies and 8658 (10.9%) women had undergone one previous cesarean; 1433 (16.6%) underwent a trial of labor after cesarean (TOLAC). Of them, 974 (68.0%) had a successful VBAC, whereas 459 (32.0%) did not. Factors significantly associated with VBAC success were as follows: a prior vaginal delivery; pregnancy weight gain ⩽ 30 lbs; Caucasian race; and labor augmentation. CONCLUSION: High-risk women with one prior cesarean are unlikely to undergo a TOLAC, but have a high rate of VBAC. Journal of Perinatology (2015) 35, 252–257; doi:10.1038/jp.2014.196; published online 23 October 2014

INTRODUCTION TOLAC and those with VBAC (Table 2). Pregnancy weight gain was ‘ ’ ‘ ’ ‘ ’ The NIH Consensus Development Conference Statement on categorized as under , met or exceed Institute of Medicine (IOM)- recommended weight gain as per the patient’s individual prepregnancy vaginal birth after cesarean (VBAC) published in March 2010 BMI class. There were minimal missing data on the variables of interest: identified a critical knowledge gap in potential access to and o 1 0.1% missing data on the delivery method and 5% missing for other availability of a trial of labor owing to provider perceptions. covariables used in the logistic regression model. Women with a high risk for comorbid conditions such as obesity, Statistical analyses were performed using STATA Release 12 software hypertension or diabetes may be considered poor candidates (StataCorp, College Station, TX, USA). Demographic characteristics of the for VBAC and therefore less likely to be offered or desirous two groups were analyzed using unpaired Student t-tests for continuous 2 of attempting a trial of labor (TOLAC). They are also the group of variables (maternal age, BMI, gestational age and birth weight) and χ -tests for categorical variables. Multivariate logistical regression was performed women most likely to develop a surgical complication such as fl wound infection, separation or a venous thromboembolic event to estimate the relative in uence of these characteristics on VBAC. 2–10 A full regression model of all factors with significant differences noted in following cesarean delivery. Therefore, identifying the sub- bivariate analyses was constructed. Sequential backward selection yielded group of women with these comorbid conditions who are most a final model of statistically influential and biologically plausible covariates. likely to have a VBAC following a trial of labor may minimize Outcome differences are reported as crude odds ratios (OR) and adjusted post-partum complications in this particularly high-risk group of OR with 95% confidence intervals (CIs). Comparisons of characteristics with – parturients.2 10 The aim of this study was to address this associated P-value o0.05 and a 95% CI not inclusive of the null value were knowledge gap and evaluate factors associated with an increased considered statistically significant. We constructed a receiver–operator likelihood of VBAC in high-risk women who attempt a trial of labor characteristic curve from the factors identified in the logistic regression after one cesarean. model and calculated the area under the curve. This study was approved by the Ohio Department of Health and Human Subjects Institutional Review Board and a de-identified data set of birth certificate data was provided by the Child Policy Research Center of METHODS Cincinnati Children’s Hospital Medical Center. This study was exempt from We performed a retrospective population-based cohort study of all eligible review by the Institutional Review Board at the University of Cincinnati, singleton live births that occurred in Ohio in 2006 and 2007. The goal of Cincinnati, OH, USA. the study was to identify factors associated with VBAC in high-risk women. Women were defined as being of high risk if they had any one or more of the following factors: hypertension (chronic, gestational hypertension or RESULTS preeclampsia), diabetes (gestational or pregestational) or a prepregnancy ⩾ There were 308 380 live births in Ohio in 2006 and 2007. After body mass index (BMI) 30. The exposure variable was trial of labor after o cesarean in a cohort of high-risk women and the outcome was VBAC. exclusion of deliveries at gestational age 20 weeks or Demographic, social, medical and prenatal factors were compared 442 weeks, births with congenital anomalies and multifetal between low-risk and high-risk women (Table 1). The same baseline gestations, there were 280 882 births available for analysis. Our characteristics were then compared between high-risk women with failed analysis was limited to women with one prior cesarean delivery

1Division of Maternal-Fetal Medicine and Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, Cincinnati, OH, USAand2Center for Prevention of Preterm Birth, Perinatal Institute Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA. Correspondence: Dr J Regan, University of Cincinnati College of Medicine, Department of Obstetrics and Gynecology, Medical Sciences Building, Room 4560, 231 Albert Sabin Way, Cincinnati 45267 0526, OH, USA. E-mail: [email protected] Presented at the Society for Gynecological Investigation 59th Annual Meeting, San Diego, CA, USA, 21–24 March 2012. Received 3 December 2013; revised 22 June 2014; accepted 3 September 2014; published online 23 October 2014 VBAC success in high-risk women J Regan et al 253

Table 1. Demographic characteristics of high-risk women vs low-risk Table 2. Demographic characteristics of high-risk women who women who had one prior cesarean (n = 22 117) attempted TOLAC (n = 1433)

Characteristic High-risk Low-risk P-value Characteristic VBAC Failed TOLAC P-value women women n = 974 n = 459 n = 8658 n = 13 459 Age Age Age 29 (25,34) 29 (25,33) 0.439 Age 29 (25,33) 29 (25,33) 0.470 Teen (o18 years) 1 (0.1) 2 (0.4) 0.405 Teen (o18 years) 22 (0.25) 70 (0.52) 0.011 18–34 years 762 (78.2) 362 (78.9) — 18–34 years 6936 (80.1) 10 735 (79.8) — AMA (⩾35 years) 211 (21.7) 95 (20.7) — AMA (⩾35 years) 1700 (19.6) 2652 (19.7) — Race Race Caucasian 649 (67.2) 278 (60.7) 0.079 Caucasian 6.530 (75.8) 10 628 (79.3) o0.001 Black 260 (26.9) 152 (33.2) — Black 1597 (18.5) 1786 (13.3) — Hispanic 41 (4.2) 18 (3.9) — Hispanic 347 (4.0) 564 (4.1) — Cigarette use 168 (17.9) 70 (15.3) 0.230

Social factors Social factors Married 5894 (68.2) 9483 (70.6) o0.001 Married 624 (64.1) 289 (63.0) 0.668 High school education 7478 (86.9) 11 586 (86.4) 0.267 High school education 769 (79.9) 381 (83.9) 0.073 Medicaid 2.995 (34.6) 3884 (28.9) o0.001 Medicaid 353 (39.4) 176 (41.1) 0.539 Private insurance 4734 (54.7) 8114 (60.3) o0.001 Private insurance 437 (44.9) 220 (47.9) 0.277 Cigarette use 1550 (18.1) 2471 (18.4) 0.546 Pregnancy factors Pregnancy factors Labor induction 246 (25.3) 87 (19) 0.008 Labor induction 408 (4.7) 660 (5.0) 0.530 Labor augmentation 229 (23.6) 70 (15.3) o0.000 Labor augmentation 377 (4.4) 818 (6.1) o0.001 Parity 3 (2,4) 2 (2,3) 1.000 Parity 2 (2,3) 2 (2,3) 0.219 Gestational age (weeks) at 38.03 (2.51) 38.03 (2.65) 0.499 Gestational age (weeks) 38.0 (2.20) 38.1 (2.05) o0.001 delivery at delivery Birth weight (g) 3291 (724) 3387 (651) 0.016 Birth weight (g) 3371 (695) 3304 (576) 1.000 Term 672 (85.7) 326 (84.5) 0.568 Term 6119 (86.4) 9718 (88.9) o0.001 Preterm (o37 weeks) 151 (15.5) 69 (15.0) 0.818 Preterm (o37 weeks) 1200 (13.9) 1461 (10.9) o0.001 Prior vaginal delivery 557 (60.0) 157 (35.3) o0.000 Prior vaginal delivery 2346 (27.1) 3782 (28.1) 0.130 Pregnancy weight gain Pregnancy weight gain Under IOM guidelines 243 (25.7) 76 (17.1) 0.002 Under IOM guidelines 1864 (22.2) 2255 (16.9) o0.001 Met IOM guidelines 220 (23.3) 116 (26.1) — Met IOM guidelines 1967 (23.4) 6256 (46.8) — Exceed IOM guidelines 483 (51.1) 253 (56.9) — Exceed IOM guidelines 4568 (54.4) 4875 (36.4) — Mean pregnancy weight 23.1 (21.3) 25.2 (22.9) 0.091 Mean pregnancy weight 24.7 (21.2) 33.7 (16.6) o0.001 gain (lbs) gain (lbs) PNC PNC No PNC 19 (2.2) 8 (2.0) 0.826 No PNC 99 (1.6) 212 (1.8) 0.007 Limited PNC 125 (14.4) 35 (8.7) 0.005 Limited PNC 596 (7.7) 1073 (9.0) 0.002 WIC 413 (42.8) 203 (45.2) 0.403 WIC 3601 (42.1) 4242 (31.7) o0.001 Abbreviations: AMA, advanced maternal age; ICU, Intensive care unit; Abbreviations: AMA, advanced maternal age; IOM, Institute of Medicine; IOM, Institute of Medicine; PNC, prenatal care; WIC, women, infants and PNC, prenatal care; WIC, women, infants and children. Limited PNC, children; TOLAC, trial of labor after cesarean. Limited PNC, o5 visits. deﬁned in vital statistics birth records as o5 PNC visits. Continuous Continuous variables are presented as mean ± s.d. or median (interquartile variables are presented as mean ± s.d. or median (interquartile range). range). Dichotomous variables are presented as number (percent). Dichotomous variables are presented as number (percent).

(n = 23 650, 11.9%). Of them, 8658 (36.6%) were defined as high- cesarean and 16.6% attempted TOLAC. Of the high-risk women risk women. There were missing data on those high-risk who attempted TOLAC, 68.0% achieved VBAC and 32.0% conditions for 1533 (6.5%) women. The remaining 13 459 women failed TOLAC. were considered low-risk for the purposes of this analysis, Figure 1. Compared with low-risk women, high-risk women were similar Of the women with one prior cesarean delivery, the defined high- in age but more likely to be of Black race, Table 1. They were more likely to be unmarried, and have WIC, Medicaid or limited prenatal risk patients were singleton gestations in women who had at least fi ⩾ care. Limited prenatal care is de ned in vital statistics birth records one of the following high-risk factors: prepregnancy BMI 30, o fi as 5 prenatal visits. These high-risk women were also more hypertension, or diabetes. This resulted in a nal cohort of 8658 likely to have a higher rate of preterm birth. They also had a higher high-risk women for analysis. fi rate of exceeding the IOM guidelines for weight gain in pregnancy Of those 8658 women de ned as being of high-risk, 6.0% had for their individual prepregnancy BMI class. Parity, gestational age hypertension only; this included individuals who had chronic and frequency of prior vaginal delivery were similar between the hypertension, gestational hypertension or preeclampsia. Of the high-risk and low-risk women. No significant differences between remaining high-risk women, 8.0% had pre-existing diabetes or high-risk women and low-risk women were noted in maternal gestational diabetes, 63.0% had a BMI ⩾ 30 and 22.0% had more delivery morbidities concerning blood transfusion, ruptured than two of the high-risk conditions. Of those high-risk women uterus, unplanned hysterectomy or admission to the intensive with one prior cesarean, 83.4% underwent an elective repeat care unit (Table 3).

Total births N=308,380 GA<20 weeks N=144

GA> 42 weeks N=15,074

Congenital Anomalies N=879

Multifetal N=10,901

Singleton Pregnancies Missing N=500 N=280,882

One previous cesarean section N=23,650 (11.9%) No hypertension, diabetes, or BMI < 30 N=13,459

Missing 1533 (6.5%) High Risk Women (HTN or DM or BMI ≥ 30) Total N=8,658 (36.6%)

Elective repeat cesarean TOLAC N=7,225 (83.4%) N=1,433 (16.6%)

Successful VBAC Failed TOLAC N=974 (68.0%) N=459 (32.0%)

Figure 1. Flow diagram of the study population.

birth. High-risk women with VBAC were more likely to have a = Table 3. Demographic characteristics of high-risk women (n 8658) limited quantity of prenatal care visits than those with a failed = vs low-risk women who had one prior cesarean (n 13 459) TOLAC. High-risk women who achieved VBAC were almost twice Characteristic High-risk women Low-risk women P-value as likely to have had a prior vaginal delivery (60.0 vs 35.3%, n = 8658 n = 13 459 Po0.001) compared with those with a failed TOLAC. The rate of VBAC in low-risk women was 79.9% (23.1% failure rate), compared Maternal morbidities with the rate of VBAC in high-risk women, which was 68.0% Blood transfusion 27 (0.2) 16 (0.2) 0.794 Ruptured uterus 11 (0.1) 13 (0.1) 0.502 (32.0% failure rate). Unplanned hysterectomy 9 (0.1) 9 (0.1) 0.345 Multivariable logistic regression identified factors associated Admission to ICU 21 (0.2) 14 (0.1) 0.011 with VBAC in this high-risk population (Table 4). The factor most significantly associated with VBAC in high-risk women who Abbreviation: ICU, Intensive care unit. Continuous variables are presented ± attempted TOLAC was prior vaginal delivery. Weight gain as mean s.d. or median (interquartile range). Dichotomous variables are ’ presented as number (percent). exceeding the IOM s recommended amount of weight gain during pregnancy for the individual’s specific prepregnancy BMI classification was found to negatively influence the likelihood of achieving VBAC. Factors not significantly associated with VBAC in Table 2 shows the differences between high-risk women who high-risk women were as follows: Caucasian race, augmentation of had a VBAC and those who had a failed TOLAC. Ages and race labor, education, type of insurance, birth weight, maternal age, distributions were similar between the groups. There were also no gestational age, cigarette smoking and marital status. The significant differences in parity, social factors or gestational age at influence of prior vaginal delivery and pregnancy weight gain

Journal of Perinatology (2015), 252 – 257 © 2015 Nature America, Inc. VBAC success in high-risk women J Regan et al 255 Interestingly, we found that exceeding the IOM pregnancy weight Table 4. Factors associated with VBAC success in high-risk women gain guidelines for prepregnancy BMI classification is negatively who undergo TOLAC, n = 1433 associated with VBAC in this high-risk population. The following Crude OR aOR factors did not appear to be associated with VBAC: Caucasian race, (95% CI) (95% CI) maternal age, marital status, medical insurance type, cigarette usage, birth weight and gestational age. Despite perceptions in Factors associated with VBAC this particular population with known increased risks associated Prior vaginal delivery, n = 714 2.75 (2.17–3.47) 3.53 (1.93–6.44) Exceed IOM guidelines, n = 147 0.48 (0.27–0.86) 0.47 (0.26–0.87) with a TOLAC, including uterine rupture, blood transfusion, endo- metritis and operative injury,2–5 our findings regarding the success Factors not associated with VBAC rates of TOLAC in this high-risk population are encouraging. = – – High school education, n 1150 0.76 (0.57 1.03) 2.31 (0.91 5.92) Patient selection in this high-risk subset could optimize VBAC Labor augmentation, n = 299 1.71 (1.28–2.30) 1.59 (0.67–3.76) Married, n = 913 1.05 (0.84–1.32) 1.22 (0.51–2.91) and therefore minimize complications associated with a failed Gestational age (weeks) 1.00 (0.95–1.04) 1.07 (0.94–1.23) TOLAC. Carefully selecting those high-risk women most likely to at delivery achieve VBAC could prevent some of the serious complications Birth weight (g) 0.61 (0.16–2.28) 1.00 (1.00–1.00) = – – known to be associated with surgery in this high-risk population, Private insurance, n 657 0.88 (0.71 1.10) 0.99 (0.42 2.32) 6–9 Maternal age (years) 0.83 (0.43–1.62) 0.94 (0.89–1.00) including, but not limited to, infectious morbidity of up to 53.0%. Caucasian, n = 927 1.15 (0.92–1.46) 0.65 (0.32–1.35) Several published studies have reported that women with some Cigarette use, n = 238 1.09 (0.98–1.22) 0.52 (0.21–1.30) individual high-risk conditions have a decreased rate of VBAC.3,9–12 Specifically, women with preeclampsia,13 pregestational and Abbreviations: aOR, adjusted odds ratio; IOM, Institute of Medicine; OR, 14–18 odds ratio; TOLAC, trial of labor after cesarean; VBAC, vaginal birth after gestational diabetes, obese women and those with excessive 6–12 cesarean. pregnancy weight gain have been reported to have higher rates of failed TOLAC compared with low-risk women. Interpreta- tion and generalization of these prior reports in counseling women with these individual risk factors may be limited, as many 1.00 high-risk women have a combination of these risk factors rather than one alone, as we found in our study. Our study concurs with findings reported in other studies that certain demographic factors are associated with a higher 0.75 likelihood of VBAC, with prior vaginal birth being the strongest associated factor.11,12 A number of previously published studies have assessed the association between individual high-risk 6–10,13–21 0.50 conditions such as diabetes, preeclampsia and obesity with VBAC. Our study differs from those in which our primary aim Sensitivity was to identify other concomitant factors that may increase the likelihood of VBAC in this group of women who are unlikely to 0.25 be offered or encouraged a VBAC. In addition, we found that exceeding the IOM guidelines for prepregnancy BMI was negatively associated with VBAC within this subset of high-risk women, a finding that has not been previously reported. Despite 0.00 public perception and decreasing support for TOLAC, our data 0.00 0.25 0.50 0.75 1.00 suggest that VBAC may be a safe and viable option for women 1 - Specificity with high-risk conditions of hypertension, diabetes and/or obesity, Area under ROC curve = 0.6864 especially in the presence of a prior vaginal birth and adherence to the IOM guidelines for weight gain during pregnancy.22 Figure 2. Receiver–operator characteristic curve generated from the logistic regression model of factors associated with VBAC in high- In our cohort of high-risk patients who attempted a trial of labor risk women. following one cesarean, the frequency of morbidities was reported to be similar to that of low-risk women with regard to uterine rupture, blood transfusion, unplanned hysterectomy as well as exceeding IOM recommendations had a similar magnitude and intensive care unit admission between women who had a VBAC direction of effect on VBAC success when stratified by separate and those with a failed TOLAC. However, adequate representation high-risk categories (hypertension, diabetes or obesity separately), of true outcomes is difficult to ascertain from birth certificate data, compared with the composite high-risk group combining the and the low frequency of reported maternal morbidities with three risk groups (data not shown). possible under-reporting diminishes the power to detect a notable The graphic receiver–operator characteristic curve generated effect. Therefore, no conclusions should be inferred from these from the logistic regression model represented in Table 4 is rare outcomes. presented in Figure 2. This combination of factors has poor The large sample size and population-based nature are predictive accuracy of VBAC in high-risk women, with an area significant strengths of this study. Our study included over 1400 under the curve of 0.686. high-risk women who attempted a TOLAC. Despite the low frequency of TOLAC in high-risk women (16.6%), the large sample size of our cohort allowed for a thorough assessment of individual DISCUSSION factors associated with VBAC in this subgroup of women. We feel We found that few high-risk women with hypertension, diabetes that, despite the possibility of selection and misclassification or obesity attempted a trial of labor after one prior cesarean (only biases, our outcome variables are relatively reliable as the rates of 16.6% (95% CI 15.8–17.4%)). Despite this, of the high-risk women scheduled repeat cesarean, VBAC and failed TOLAC in our study who attempted a TOLAC, the rate of achieving VBAC was high are comparable to the rates overall reported in the US and to the (68.0% (95% CI 65.5–70.4%)). After accounting for the other US national averages.1 The limitations of the study include those influential demographic and pregnancy-related risks, we found inherent to studies derived from vital statistics data.23–30 that a prior vaginal birth was the strongest influence on VBAC. Misclassification or under-reporting of certain outcomes, such as

© 2015 Nature America, Inc. Journal of Perinatology (2015), 252 – 257 VBAC success in high-risk women J Regan et al 256 complications of delivery and whether or not someone intended 4 Macones GA, Peipert J, Nelson DB, Odibo A, Stevens EJ, Stamilio DM et al. to have a TOLAC, could bias results toward the null hypothesis or Maternal complications with vaginal birth after cesarean delivery: a overestimate effect estimates. Comorbidities also may be poorly multicenter study. Am J Obstet Gynecol 2005; 193(5): 1656–1662. recorded, which can introduce bias, most likely toward the null. 5 Fitzpatrick KE, Kurinczuk JJ, Alfirevic Z, Spark P, Brocklehurst P, Knight M. Uterine Another limitation inherent to our data source is that it is not rupture by intended mode of delivery in the UK: a national case-control study. PLos Med 2012; 9(3): e101184. possible to ascertain how individual physician practice styles may 6 Juhasz G, Gyamfi C, Gyamfi P, Tocce K, Stone JL. Effect of body mass index and affect TOLAC. For this study, we chose exposure (mode of delivery) excessive weight gain on success of vaginal birth after cesarean delivery. Obstet and outcome (VBAC in high-risk patients) variables with minimal Gynecol 2005; 106(4): 741–746. missing data and with frequencies comparable to those in the 7 Chauhan SP, Magann EF, Carroll CS, Barrilleaux PS, Scardo JA, Martin JN Jr. Mode published literature. Therefore, we believe our results are general- of delivery for the morbidly obese with prior cesarean delivery: vaginal versus izable, despite the knowledge that not all biases can be repeat cesarean section. Am J Obstet Gynecol 2001; 185(2): 349–354. thoroughly assessed. 8 Carroll CS Sr, Magann EF, Chauhan SP, Klauser CK, Morrison JC. Vaginal birth after Cesarean delivery rates have reached an all-time high.1,12 The cesarean section versus elective repeat cesarean delivery: weight-based out- 188 – influence of provider perceptions in certain high-risk populations comes. Am J Obstet Gynecol 2003; (6): 1516 1520. fi 9 Hibbard JU, Gilbert S, Landon MB, Hauth JC, Leveno KJ, Spong CY et al. Trial of are dif cult to measure, but selection of the best candidates for labor or repeat cesarean delivery in women with morbid obesity and previous TOLAC based on individual factors within this subset may increase cesarean delivery. Obstet Gynecol 2006; 108(1): 125–133. the likelihood of a successful outcome in women with a prior 10 Durnwald CP, Ehrenberg HM, Mercer BM. The impact of maternal obesity and cesarean. Women with hypertension, diabetes and obesity who weight gain on vaginal birth after cesarean section success. Am J of Obstetrics undergo repeat cesarean are at the highest risk of adverse Gynecol 2004; 191(3): 954–957. outcome related to risk of hemorrhage, prolonged operative 11 Landon M, Leindecker S, Spong CY, Hauth JC, Bloom S, Varner MW et al. The MFM times, postoperative febrile illness, thromboembolic events and Cesarean Registry: Factors affecting the success of trial of labor after previous 193 – wound complications and infection.18 Identifying a population cesarean delivery. Am J of Obstet Gynecol 2005; (3 Pt 2): 1016 1023. that is most likely to be successful regarding TOLAC may 12 Shanks AL, Cahill AG. Delivery after prior cesarean: success rate and factors. Clin Perinatol 2011; 38(2): 233–245. ultimately yield a lower overall rate of maternal morbidity in 13 Srinivas SK, Stamilio DM, Stevens EJ, Peipert JF, Odibo AO, Macones GA et al. women with these high-risk conditions. 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