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Preterm Birth Or Small for Gestational Age in a Singleton Pregnancy and Risk of Recurrence in a Subsequent Twin Pregnancy

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Preterm Birth Or Small for Gestational Age in a Singleton Pregnancy and Risk of Recurrence in a Subsequent Twin Pregnancy Original Research Preterm Birth or Small for Gestational Age in a Singleton Pregnancy and Risk of Recurrence in a Subsequent Twin Pregnancy Nathan S. Fox, MD, Erica Stern, BA, Simi Gupta, MD, Daniel H. Saltzman, MD, Chad K. Klauser, MD, and Andrei Rebarber, MD OBJECTIVE: To evaluate whether a history of preterm associated with recurrence of the same condition in birth or small for gestational age (SGA) in a singleton a subsequent twin pregnancy. pregnancy is associated with an increased risk of recur- CONCLUSION: Prior preterm birth and SGA in a single- rence of the same condition in a subsequent twin ton pregnancy increase the risk of the same condition in pregnancy. a subsequent twin pregnancy. We postulate that the METHODS: Retrospective cohort study of twin preg- extrinsic mechanism responsible for the pathophysiology nancies delivered in one maternal–fetal medicine prac- of adverse outcomes in twin pregnancies overlaps with tice from 2005 to 2014. Patients with a history of that in singleton pregnancies. singleton preterm birth at less than 37 weeks of gestation (Obstet Gynecol 2015;125:870–5) were compared with patients with a history of singleton DOI: 10.1097/AOG.0000000000000741 term birth and nulliparous patients. A similar analysis was LEVEL OF EVIDENCE: II performed for a history of SGA (birth weight less than 10%). he incidence of twin pregnancy in the United RESULTS: Six hundred forty-seven twin pregnancies TStates has grown from 1.9% of live births in were included. The prior singleton gestational age at 1980 to 3.3% in 2011.1 Twins are at increased of mor- delivery was significantly positively correlated with the bidity and mortality when compared with singletons P, twin gestational age at delivery ( .001), and the prior resulting from the high incidence of preterm birth and singleton birth weight was significantly positively corre- small for gestational age (SGA) in this population. In lated with the birth weight of the larger twin (P,.001) and the smaller twin (P,.001). The rate of twin preterm the United States, 57.3% of twins are born preterm birth before 32 weeks of gestation was 3.5% in patients (less than 37 weeks of gestation) and 11.3% are born 2 with a prior term birth, 9.2% in nulliparous patients, and before 32 weeks of gestation. This leads to an 26% in patients with a prior preterm birth (P,.001). The increased incidence of low birth weight and compli- rate of SGA in patients with a prior birth not complicated cations from prematurity in twins. Furthermore, even by SGA was 42.1%, in nulliparous women it was 54.4%, when adjusted for gestational age, twins have an and in patients with a history of SGA it was 65.2% increased incidence of SGA with studies reporting (P5.007). On regression analysis, prior preterm birth an incidence of 15–25%.3–5 Based on more contempo- and SGA of a singleton pregnancy were independently rary data, we have recently reported an even higher incidence of SGA with 47% of patients delivering a neonate less than the 10th percentile for gestational From the Maternal Fetal Medicine Associates, PLLC, and the Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at age and 27% of patients delivering a neonate less than Mount Sinai, New York, New York. the fifth percentile for gestational age.6 Corresponding author: Nathan S. Fox, MD, Maternal Fetal Medicine Associates, In singleton pregnancies, there is an established PLLC, 70 East 90th Street, New York, NY 10128; e-mail: [email protected]. relationship between outcomes of prior pregnancies Financial Disclosure on future pregnancies. Specifically, patients with The authors did not report any potential conflicts of interest. a prior preterm birth are at increased risk for © 2015 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved. recurrent preterm birth and this association is stronger ISSN: 0029-7844/15 with earlier gestational ages at the prior preterm 870 VOL. 125, NO. 4, APRIL 2015 OBSTETRICS & GYNECOLOGY Copyright ª by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. birth.7–9 Similarly, patients with prior SGA neonates gestation as well as mean birth weight of the larger or fetal growth restriction are at increased risk of twin, mean birth weight of the smaller twin as well as recurrence as well.10–12 In regard to the relationship a birth weight less than the 10th percentile for gesta- between twin and singleton pregnancy outcomes, tional age and a birth weight less than the fifth per- most research has focused on the effect or a prior twin centile for gestational age. To define birth weight adverse outcome on a future singleton pregnancy out- percentiles for gestational age in twins, we used stan- come. For example, there is debate in the literature dard tables for singleton pregnancies.19 We chose sin- whether a prior twin preterm birth is or is not a risk gleton tables because they are the standard tables used factor for subsequent preterm birth in a singleton for twins in the United States in defining growth pregnancy.8,13–15 restriction and determining neonatal outcomes.6,20–22 There are fewer data regarding the risk of a prior Forpatientswhosepriorsingletonbirthwas20–23 6/7 singleton pregnancy outcome on subsequent twin weeks of gestation, we did include them as having a prior pregnancy outcomes and much of these data are preterm birth, but we did not consider the birth weight derived from statewide registries16,17 as opposed to in regard to SGA and excluded these pregnancies from single centers.18 Furthermore, the data on this ques- the SGA analysis. tion do not include patients with twin pregnancies and Gestational age was determined by last menstrual no previous pregnancies. The objective of our study period and confirmed by ultrasonography in all was to evaluate whether a history of preterm birth or patients. The pregnancy was redated if there was SGA in a singleton pregnancy is associated with an a greater than 5-day discrepancy up to 14 weeks of increased risk of recurrence of the same condition in gestation or a greater than 7-day discrepancy after 14 a subsequent twin pregnancy. weeks of gestation. If the pregnancy was the result of in vitro fertilization (IVF), gestational age was deter- MATERIALS AND METHODS mined from IVF dating. In our practice, patients with After Biomedical Research Alliance of New York twin pregnancies are managed according to a standard institutional review board approval was obtained, the protocol, regardless of their obstetric history. We do charts of all patients with twin pregnancies 22 weeks not administer progesterone to twins with a prior of gestation or greater delivered by a single maternal- singleton preterm birth. All patients with twin preg- fetal medicine practice between June 2005 (when our nancies in our practice undergo serial growth ultra- electronic medical record was established) and June sonograms every 2–4 weeks and weekly biophysical 2014 were reviewed. Baseline characteristics and profile testing beginning at 32 weeks of gestation or pregnancy outcomes were obtained from our com- more frequently as indicated. Dichorionic twin preg- puterized medical record. We excluded pregnancies nancies are delivered at 38 weeks of gestation and complicated by twin–twin transfusion syndrome, monochorionic twin pregnancies are delivered at 37 major fetal anomalies, and patients with monochor- weeks of gestation, or earlier as indicated. ionic–monoamniotic placentation. Pearson correlation and one-way analysis of We reviewed the obstetric history of all our twin variance were used when appropriate (Stata 11). pregnancy patients. For patients who were not nullip- Accompanying each analysis of variance, we also arous, we used the most recent singleton pregnancy conducted Bartlett’s test for equal variances, which outcome for analysis. If the patient’s most recent preg- showed variances to be unequal (P,.01 for all varia- nancy was a twin pregnancy, they were excluded from bles), so we used the Kruskal-Wallis test for analysis analysis. We recorded the prior singleton gestational and to analyze whether means differed by categories. age at delivery as well as whether that delivery was This test, because it is nonparametric, does not require preterm, defined as delivery at less than 37 weeks of that variances are equal between categories nor does it gestation from any cause. We also recorded the prior presume the data are normally distributed. singleton birth weight as well as whether that preg- To estimate the independent association between nancy was complicated by SGA, defined as a birth prior pregnancy history and outcomes, we performed weight less than the 10th percentile for gestational a logistic regression analysis controlling for advanced age.19 We estimated the association of these prior sin- maternal age (35 years or older at delivery), obesity gleton pregnancy outcomes with preterm birth and (body mass index [calculated as weight (kg)/[height SGA in the index twin pregnancy. We analyzed sev- (m)]2] 30 or higher), chorionicity, IVF, multifetal eral gestational age outcomes, including mean gesta- reduction, maternal race, prior loop electrosurgical tional age at delivery and delivery at less than 37, less excision procedure or cone biopsy, gestational dia- than 34, less than 32, and less than 28 weeks of betes, preeclampsia, anticoagulation, and uterine VOL. 125, NO. 4, APRIL 2015 Fox et al Obstetric History and Subsequent Pregnancy Outcome 871 Copyright ª by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. anomaly. The regression was done in a backward correlated with the birth weight of the larger twin stepwise fashion including variables with a significance (Pearson correlation coefficient 0.353, P,.001) as well to the level of ,.10.
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