Twin pregnancies account for approximately 3% of all births in the United States, as in France.1,2 In the absence of contraindications, it is recommended that women with a cephalic first twin be offered vaginal delivery, provided personnel with appropriate training and experience are available, because the most relevant recent data show no differences in neonatal mortality and morbidity according to the planned mode of delivery.3,4 Conversely, when the first twin is in breech presentation, American and British guidelines recommend planned cesarean delivery.5,6 Although several retrospective studies have failed to show that higher neonatal mortality and morbidity are associated with planned vaginal delivery of first twins in breech presentation,7–13 the conclusions of these guidelines rest on the low level of evidence and insufficient statistical power of these reassuring studies and on the extrapolation of the results of the Term Breech Trial in singleton pregnancies to twin pregnancies with a breech-presenting first twin.14 Consequently, despite the lack of solid evidence, planned vaginal delivery has been progressively abandoned, resulting, as in the delivery of breech singletons,15–17 in a loss of expertise in the delivery of twin pregnancies with a first twin in breech presentation.18
The national prospective JUMODA (JUmeaux MODe d'Accouchement) study, specially designed to assess the management of twin births, took place in a country where clinical guidelines state that planned cesarean and planned vaginal delivery are two possible options in this situation19 and where obstetricians are trained in and accustomed to the management of vaginal breech delivery.20 Therefore, the aim of this planned secondary analysis of the JUMODA cohort was to obtain higher-quality evidence by comparing neonatal mortality and morbidity according to the planned mode of delivery of first twins in breech presentation. As previously reported in two French retrospective studies,7,8 we hypothesized that planned vaginal delivery will not be associated with a significant increase in neonatal mortality and morbidity as compared with planned cesarean delivery.
The JUMODA study was a nationwide, observational, prospective, population-based cohort study conducted from February 10, 2014, to March 1, 2015, in France. Detailed information about the participating women and maternity units has previously been reported.3 Briefly, this cohort was specially designed to assess the effect of the mode of delivery on neonatal outcomes in twin pregnancies at or after 22 weeks of gestation (N=8,823 pregnancies included).
In view of the absence of solid evidence supporting one management policy over the other, French guidelines allow both planned cesarean and planned vaginal delivery when the first twin is in breech presentation before or at term, depending on the situation.19 According to the guidelines of the National College of French Gynecologists and Obstetricians,21 to plan a vaginal delivery for singletons in breech presentation as well as for twin pregnancy with a first twin in breech presentation, it is recommended that the following criteria be met: normal computed tomographic pelvimetry, no hyperextension of the fetal head (checked by ultrasonography), estimated fetal weight of less than 3,800 g (with clinical and ultrasound examinations), continuous electronic fetal heart rate monitoring during labor, and the woman’s informed consent after explanations about benefits and risks of both planned modes of delivery. Finally, the type of breech presentation (complete or frank) and the presentation of the second twin are not taken into account in the decision of the planned mode of delivery in our country.
To conduct this analysis, we selected first twins in breech presentation. Then, to select only low-risk pregnancies, we applied all of the inclusion and exclusion criteria of the Twin Birth Study, except the criterion for first-twin presentation (Fig. 1).4 Exclusion criteria were twin pregnancy at less than 32 0/7 weeks of gestation, neonates with birth weights of less than 1,500 g or more than 4,000 g, monoamniotic twins, fetal reduction at 13 or more weeks of gestation, a severe fetal anomaly affecting either twin, second twin substantially larger than the first twin, and more than one previous lower segment cesarean delivery. Others exclusion criteria were myoma in the lower uterine segment or placenta previa overlying the internal os, as indications for planned cesarean delivery, and home deliveries.
The exposure of interest was the planned mode of delivery, and the group with planned cesarean deliveries was chosen as the reference because it is the mode of delivery recommended by the American College of Obstetricians and Gynecologists and the Royal College of Obstetricians and Gynaecologists.5,6 The planned mode of delivery was defined prospectively by the obstetrician who performed the delivery. Immediately after delivery, obstetricians completed a detailed web-based questionnaire about planned mode of delivery, indications for planned cesarean delivery, and details about management of delivery and then classified them as planned cesarean or planned vaginal deliveries. Research nurses collected data about maternal characteristics, medical history, pregnancy complications, and neonatal health.
The primary outcome was a composite of intrapartum mortality and neonatal mortality and morbidity, as already published,3,22,23 very similar to the primary outcome of the Twin Birth Study.4 Neonatal mortality was assessed during the first 28 days of life. Neonatal morbidity was defined as one or more of the following: 5-minute Apgar score of less than 4; birth trauma (humerus, femur, or skull fracture; spinal cord injury; or brachial plexus palsy); injury of the phrenic or facial nerve present at 72 hours of age or at hospital discharge; subdural or intracerebral hemorrhage (confirmed by ultrasonography, computed tomography, or magnetic resonance imaging); encephalopathy according to the Sarnat classification24; seizures on at least two occasions before 72 hours of age; endotracheal ventilation within 72 hours after birth for at least 24 hours; proven neonatal sepsis during neonatal hospitalization, defined by a positive blood culture or cerebrospinal fluid culture; bronchopulmonary dysplasia, defined as the need for supplemental oxygen at a postnatal gestational age of 36 weeks; grade III and IV intraventricular hemorrhage or cystic periventricular leukomalacia confirmed by ultrasonography; and stage II and III necrotizing enterocolitis according to Bell staging.25 This primary outcome was treated as a binary variable.
We first compared the characteristics of the women and their pregnancies, labors, hospitals and neonates in the two groups and tested the differences with χ2 or Fisher exact tests for categorical variables and student or Wilcoxon rank sum tests for quantitative variables, as appropriate. To assess the association between planned mode of delivery and neonatal mortality and morbidity, while controlling for confounding factors, we used a multivariate Poisson regression model with a robust variance calculation method to estimate relative risks (RR) and 95% CIs, with a random intercept to take variability between centers into account.26 Potential confounders were selected from the literature and included parity, previous cesarean delivery, gestational age at delivery, and annual number of twin deliveries per center.
To control for indication bias related to confounding factors that might influence both the choice of the planned mode of delivery and the occurrence of neonatal mortality and morbidity, we used a propensity score approach. The propensity score was defined as the probability of a planned vaginal delivery based on covariates. A propensity score was estimated for all pregnancies by a logistic regression model with planned mode of delivery as the dependent variable in relation to the baseline maternal, obstetric, neonatal, and maternity-unit characteristics (variables listed in the footnote to Fig. 2). For each pregnancy, we calculated a propensity score, starting by performing a propensity-score matching analysis. Exposed (planned vaginal delivery) and unexposed (planned cesarean delivery) pregnancies were matched with a one-to-one nearest neighbor matching algorithm without replacement by the average propensity score within a caliper of 0.10.27 Unmatched pregnancies were deleted from the analysis. Imbalances after matching were checked by propensity score distribution and calculation of standardized mean differences.28 In the matched set, RRs and their 95% Cis were estimated to quantify the association between the planned mode of delivery and neonatal mortality and morbidity by generalized estimating equation multivariate Poisson regression, to account for paired data after matching on propensity score, without further adjustment. Second, the inverse probability of treatment weighting, based on the estimated propensity scores, was calculated to ascertain the validity of the results.
In a sensitivity analysis, to further limit indication bias, we restricted the planned cesarean delivery group to cesarean deliveries performed only because the first twin was in breech presentation. We similarly compared neonatal mortality and morbidity for the second twins.
The proportion of women with missing data for covariates for multivariate analysis ranged from 0% to 0.4% and for covariates of propensity score analysis from 0% to 12.1%. The 230 (15.7%) women with missing data had characteristics similar to those of the women with full data. We used multiple imputation by chained equations to handle missing data and generated 16 independent imputation data sets.
At the conventional two-tailed significance level of 0.05, with a neonatal morbidity rate of 1.9% in the planned cesarean delivery group, the post hoc power analysis showed that the available number of women in each group provided a statistical power of 80% to show a RR greater than or equal to 2.65 for quantifying the association between the planned mode of delivery and the primary outcome.
All tests were two-sided with P<.05. All analyses were performed with STATA 13.0.
The National Data Protection Authority (DR-2013-528), the consultative committee on the treatment of information on personal health data for research purposes (13-298), and the committee for the protection of people participating in biomedical research (PP-13 014) all approved this study.
Our study population included 1,467 women with a first twin in breech presentation: 1,169 (79.7%) had planned cesarean and 298 (20.3%) planned vaginal deliveries (Fig. 1). In the planned vaginal delivery group, 185 (62.1%) women delivered both twins vaginally, 110 (36.9%) underwent cesarean delivery for both twins, and three (1.0%) had cesarean delivery for the second twin after vaginal delivery of the first. In the planned cesarean delivery group, 300 (25.8%) women went into labor before the date planned and four (0.4%) delivered both twins vaginally.
Compared with women with planned cesarean deliveries, those with planned vaginal deliveries were more often parous without any previous cesarean delivery, had pregnancy complications and induced labor and delivery before 37 weeks of gestation less often, and more often gave birth in level III university hospital maternity units and in facilities with high numbers of annual twin deliveries (Tables 1 and 2).
The main indication for planned cesarean delivery was the breech presentation of the first twin, for 715 of 1,169 (61.2%) (Table 3). The main indications for cesarean delivery during labor in the planned vaginal group were failure to progress (55/113, 48.7%) and nonreassuring fetal heart rate monitoring (30/113, 26.5%).
No fetus died intrapartum. The rate of composite neonatal mortality and morbidity for first twins was similar between the planned vaginal and planned cesarean delivery groups: 5/298 (1.7%; 95% CI 0.2–3.1) compared with 22/1,169 (1.9%; 95% CI 0.1–2.7) respectively (crude RR 0.90, 95% CI 0.34–2.34) (Table 4 and Fig. 2). In both groups, mechanical ventilation and proven neonatal sepsis were the main driver of neonatal mortality and morbidity. One case of interlocking twins occurred in the planned vaginal delivery group at 37 weeks of gestation, indicating emergency cesarean delivery. The first twin had severe neonatal morbidity because of an Apgar score of less than 4 at 5 minutes. The 5-minute Apgar score of the second twin was 9. Both twins were discharged home on day 7. After adjustment for potential confounders, planned vaginal delivery was not associated with an increased risk of neonatal mortality and morbidity compared with planned cesarean delivery (adjusted RR 0.71, 95% CI 0.27–1.86).
In the propensity score matching analysis, 596 pregnancies, 298 in each group, could be matched. The matched groups were found to be well-balanced (standardized differences less than 10% except for pregnancy complications [12.7%], Appendix 2, available online at http://links.lww.com/AOG/B796). This analysis similarly found that planned vaginal delivery was not associated with an increased risk of neonatal mortality and morbidity compared with planned cesarean delivery (RR 0.61, 95% CI 0.20–1.83) (Fig. 2). Results were similar in the inverse probability of treatment weighting analysis (RR 0.63, 95% CI 0.23–1.74).
Analyses for the second twins similarly found that planned vaginal delivery was not associated with higher neonatal mortality and morbidity than was planned cesarean delivery: 7 of 298 (2.3%) compared with 28 of 1,169 (2.4%); crude RR 0.95, 95% CI 0.42–2.14; standard multivariate analysis: adjusted RR 0.76, 95% CI 0.33–1.72, matching on propensity score: RR 0.45, 95% CI 0.19–1.08, inverse probability of treatment weighting: RR 0.52, 95% CI 0.21–1.29.
The sensitivity analysis restricted to the planned cesarean deliveries performed only because the first twin was in breech presentation showed similar neonatal mortality and morbidity rates for first twins: 5 of 298 (1.7%) in the planned vaginal compared with 12 of 715 (1.9%) in the planned cesarean delivery group (crude RR 1.02, 95% CI 0.63–2.87; adjusted RR 0.66, 95% CI 0.22–1.94). Results for second twins were similar: 7 of 298 (2.4%) compared with 17 of 715 (2.5%) (crude RR 1.01, 95% CI 0.42–2.41; adjusted RR 0.58, 95% CI 0.22–1.54) in the planned vaginal and cesarean delivery groups.
This planned secondary analysis of the JUMODA study shows that when first twins are in breech presentation, planned vaginal delivery in carefully selected patients is not associated with a higher risk of neonatal mortality and morbidity for either first or second twins than planned cesarean delivery.
Our results are consistent with previous studies analyzing neonatal morbidity according to either the planned7,8 or the actual9–13 mode of delivery when the first twin is in breech presentation. Because these studies were limited by their retrospective design, poor consideration of confounding factors, and small numbers of participants, most clinical guidelines have not considered that they provide a sufficiently high quality of evidence to justify allowing planned vaginal delivery. Because breech presentation was an exclusion criterion in the Twin Birth Study, our results present the highest quality evidence thus far published and provide new arguments supporting planned vaginal delivery in twin pregnancies with a breech-presenting first twin.
Although we made no formal statistical comparison, the global neonatal mortality and morbidity rate after planned vaginal delivery in the this analysis (2% [12/596]) is similar to the rate previously reported in the low-risk population of the JUMODA cohort when the first twin is in cephalic presentation (2.0% [133/6,820]),3 for whom planned vaginal delivery is recommended. In addition, to inform women and make a shared decision concerning the planned mode of delivery, the absence of neonatal benefits associated with planned cesarean delivery in this study further emphasizes the reported increase in short-term and long-term maternal and infant risks associated with planned cesarean deliveries.29–33
The strengths of our study include its population-based cohort design and prospective enrollment, which enabled us to collect clinically pertinent data about delivery management. The planned mode of delivery was defined prospectively by the practitioners who managed the delivery, in contrast to retrospective studies in which the planned, when specified, mode of delivery was defined a posteriori. Our primary outcome was a recognized valid neonatal outcome used in previous studies analyzing neonatal morbidity in delivery of twin pregnancies.3,4,22,23 Finally, we took the confounding by indication inherent in this type of observational study into account, first by a rigorous selection of the population, by applying the Twin Birth Study selection criteria for including only low-risk women, then with a sensitivity analysis with the planned cesarean delivery group constituted only by planned cesarean deliveries performed for breech presentation as a more rigorous surrogate for planned low-risk cesarean deliveries. Second, we used diverse statistical approaches to adjust for confounding factors and a propensity score analysis to minimize the likelihood of incorrectly attributing any risk of neonatal morbidity to planned cesarean delivery.
The main limitation of our study is the small sample size of the planned vaginal delivery group, limiting our ability to show significant difference for rare events, such as mortality due to interlocking twins. Because the study was underpowered, the CIs are wide, and we could not formally exclude an increase in neonatal mortality and morbidity associated with planned vaginal delivery. Our nonsignificant results cannot therefore be generalized. Nonetheless, with a neonatal morbidity rate of 1.9% in the planned cesarean delivery group observed in this study, this analysis had a statistical power of 80% to show a 2.65-fold increase in the risk of neonatal morbidity for the first twin in the planned vaginal delivery group, that is, a rate of 4.5% (we found a rate of 1.7% in this study). Moreover, because of the observational design of this study, and despite the number of covariates available and the use of propensity score approaches, we cannot rule out possible unmeasured residual confounding. However, the only study design that would provide two comparable planned cesarean and vaginal delivery groups would be a randomized trial, which is highly unlikely to take place, given the large number of pregnancies required for inclusion and current obstetric practices. Finally, our findings can be generalized only to centers where obstetricians are trained in and accustomed to vaginal deliveries for breech presentation.
Our results have implications for clinical practice and may be useful in choosing the planned mode of delivery for pregnancies with a first twin in breech presentation. Planned vaginal delivery appears to be a reasonable option in this situation given the absence of any augmentation in the risk of neonatal mortality and morbidity after planned vaginal compared with planned cesarean delivery.
Applying these results to practitioners who may have lost or never learned the skills required for vaginal breech delivery and to residents during their initial formation requires investing in the teaching of obstetric maneuvers. Because simulation training has shown a positive effect in singleton vaginal breech deliveries by residents34 and in breech second-twin extractions,35,36 this pedagogical strategy should also be considered for training for vaginal delivery of first twins in breech presentation.
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