Twins account for 3.5% of all births in France.1 Even when the first twin is vertex, the optimal mode of delivery of twin gestations remains controversial, because of the obstetric complications that can occur after the first twin is born, ie, placental separation, cord prolapse, or fetal bradycardia of the second twin. A small randomized trial,2 in-hospital observational retrospective studies,3–7 and meta-analyses8,9 did not evidence significant increased adverse neonatal outcomes after vaginal birth of both twins in comparison with cesarean. Based on these reports, American and French Colleges of Obstetricians and Gynecologists still accept planned vaginal delivery when the first twin is in cephalic presentation.10,11 Conversely, large population-based studies showed an association between neonatal mortality and morbidity of the second twin and vaginal delivery.12–18 Some then suggest systematic planned cesarean delivery for all twin gestations could protect second twins from increased neonatal mortality and morbidity.17,18
Longer intertwin delivery intervals are correlated with poorer umbilical artery blood gas results19 and greater rates of cesarean delivery for the second twin after vaginal birth of the first twin.20–22 Cesarean delivery after the first twin is born vaginally is associated with increased neonatal mortality and morbidity of the second twin.13–15,18 Therefore, active management of second twin delivery after vaginal birth of the first twin has been proposed for reducing intertwin delivery interval, difficult obstetric maneuvers for second twin delivery, and thus cesarean delivery for the second twin and its associated complications. Policies for shortening intertwin delivery interval comprise oxytocin infusion with maternal pushing efforts23 or internal version and subsequent breech extraction24,25 when the second twin is vertex, and immediate total breech extraction23–25 or external version and subsequent cephalic delivery21,26 when the second twin is nonvertex.
Because information regarding management of second twin delivery is lacking in population-based studies, the aim of this study was to compare neonatal and maternal outcomes in a cohort of twins according to the planned mode of delivery, in a university tertiary care center routinely performing active management of second twin delivery.
MATERIALS AND METHODS
A study of twin pregnancies delivered in our university, level III maternity (3500 deliveries per year) between January 1, 1993, and December 31, 2005, was undertaken. The Committee for Protection of Person Paris Ile-de-France III has examined this work and found it conformed to the ethical standards and to the scientific requirements applicable to biomedical research. After exclusion of fetal deaths before labor and major congenital abnormalities, we included all the consecutive sets of twins born after 35 weeks of gestation with a first twin in cephalic presentation. Gestational age was established by last menstrual date and first trimester ultrasound scan. The scan date was preferred if the menstrual date was uncertain or if there was discrepancy of more than 5 days between the two estimates.
In our institution, route of delivery for twin gestation results from a collective decision taken at the daily obstetric staff meeting. Fetal positions, umbilical artery blood flows and ultrasound weight estimations must have been assessed within the week before attempted vaginal delivery. If recent ultrasound weight estimations are lacking at the beginning of labor, they are performed in the delivery room. Vaginal delivery is proposed to every woman with clinically normal pelvis without past history of cesarean delivery, as long as the second twin is not 25% larger than the first twin and the umbilical artery blood flows and fetal heart rates are normal. As previously reported,27 monoamniotic pregnancy is not a contraindication to vaginal delivery in our institution when the first twin is vertex and vaginal birth is attempted for women with grade I or II placenta previa, as long as no bleeding occurs during labor. In case of attempted vaginal birth, labor and deliveries are managed as follows: At admission in the delivery room, a large maternal intravenous access is set up. Electronic fetal heart rates are continuously monitored with a twins monitor. Epidural analgesia, in the absence of contraindication, is performed routinely. At delivery, present in the delivery room are one junior obstetrician in training, one senior obstetrician, one senior anesthesiologist, and two midwives. After the first shoulder of the first twin is delivered, oxytocin flow is stopped and 10 mL of lidocaine (Xylocaine, Astra Pharmaceuticals, Wayne PA) 2% are injected in the epidural catheter by the anesthesiologist. As soon as the first twin is born, the junior obstetrician performs the delivery of the second twin under direct supervision of the senior obstetrician (Fig. 1). In cases of breech presentation or transverse lie, immediate total breech extraction is performed as described.23 For vertex second twin, if the fetal head is above a 0 station, delivery is attempted after internal version. The hand placed in the uterus, membranes intact, follows the back, breech and legs of the fetus before grasping both feet. The feet are drawn down into the vagina while the external hand of the operator laterally repulses the fetal head for facilitating the rotation. The second twin is then delivered by total breech extraction. Only in cases of uterine hypertony, the anesthesiologist intravenously administers 100 mcg of nitroglycerine for relaxing the uterus. If the fetal head is at or below a 0 station, maternal pushing efforts are maintained, oxytocin infusion is restarted, the membranes are ruptured once the fetal head is engaged in the pelvis, and the second twin is delivered. Both neonates are brought by the midwives to the pediatricians in the adjacent room. Manual removal of the placenta is systematically performed.
Maternal and obstetric data are collected prospectively every day and recorded in our computerized database by midwifes and residents during hospitalization and immediately after delivery. Details of maternal age, parity, chorionicity, pregnancy complications, analgesia, labor induction, presentation, mode of delivery, obstetric maneuvers, and intertwin delivery interval were reviewed. Neonatal data were extracted from our computerized database and cross-matched with the neonatal intensive care unit database. The clinical notes from the paper files of all the transferred neonates are carefully examined. Neonatal composite morbidity was defined as any of the following: 5-minute Apgar score less than 4, umbilical artery pH less than 7.0, neonatal intensive care unit transfer more than 4 days, pneumothorax, fracture, and neonatal death at less than 28 days of life. Postpartum hemorrhage was defined as blood loss more than 500 mL, and severe postpartum hemorrhage as postpartum hemorrhage requiring blood transfusion, embolization, artery ligation, or hysterectomy. Maternal composite morbidity was defined as any of the following: severe postpartum hemorrhage, transfer to intensive care unit, cardiopulmonary complications as pulmonary embolism or edema, and maternal death.
The primary outcome was neonatal composite morbidity for first and second twins. The secondary outcome was maternal composite morbidity. We first compared maternal and neonatal characteristics and the outcomes of the two study populations with Pearson's χ2 test or Fisher exact test when the expected frequency was small for qualitative items. One-way analysis of variance and t tests were used for quantitative variables. We then estimated the adjusted odds ratios and their 95% confidence intervals for the primary and secondary outcomes using logistic regression models with the planned vaginal delivery group as the reference. Potential confounding variables that were entered into the regression logistic model included maternal age, parity, pregnancy complications (hypertension, preeclampsia, diabetes, twin-to-twin transfusion syndrome, and placenta previa), fetal gender, gestational age, and birth weight. Because of potential residual confounders not controlled by the logistic regression model, we performed a second analysis in which patients who experienced pregnancy complications (hypertension, preeclampsia, small for gestational age, diabetes, twin-to-twin transfusion syndrome, and placenta previa) were excluded. We used Stata 9.2 software (StataCorp LP College Station, TX).
During the study period, 758 sets of twins born after 35 weeks of gestation with a cephalic-presenting first twin delivered in our university level III maternity facility. Planned cesarean delivery was programmed for 101 (13.3%) women because of previous cesarean (n=47), previous myomectomy (n=3), placenta previa (n=5), fetal indications (n=28) (small for gestational age and twin-to-twin transfusion syndrome), maternal indications (n=9) (severe preeclampsia), both fetal and maternal (n=6) indications, or unknown (n=3) reasons. Number of twin pregnancies and rates of planned cesarean delivery did not increase significantly between the 1993–1996 (24 of 210, 11.5%) and 2002–2005 periods (38 of 224, 16.9%) (P=.10). Cesarean delivery was planned for eight of 54 (14.5%) women in 2005. Vaginal birth was attempted in 657 (86.7%) patients (Fig. 2). Among planned vaginal deliveries, 515 (78.4%) women delivered both twins vaginally, 139 (21.1%) had cesarean delivery during labor and three (0.5%) had cesarean delivery for the second twin after vaginal birth of the first twin (Fig. 2). Cesarean deliveries for the second twin resulted from failed internal version in one transverse and two cephalic-presenting second twins (Fig. 1). In the planned vaginal delivery group, labor was induced for 354 (53.9%) women because of gestational age 37 weeks or more (n=224), maternal (n=74) or fetal (n=27) indications, or preterm rupture of membranes (n=23).
As shown in Table 1, patients with planned cesarean delivery were significantly older, had a higher parity, and more previous cesarean, general anesthesia, and pregnancy complications than women in the planned vaginal delivery group. They delivered at a significantly earlier gestational age and had smaller neonates than patients in the planned vaginal delivery group (Table 1). Women having experienced at least one of the pregnancy complications listed in Table 1 were those excluded in the second analysis (n=202).
In the planned vaginal delivery group, internal version of the second twin in vertex presentation and subsequent total breech extraction was performed in almost two thirds of vertex second twins, and immediate total breech extraction for every breech-presented second twin (Table 2). Active management of second twin delivery after vaginal birth of the first twin resulted in a mean intertwin delivery interval of 4.9±3.2 minutes. Total breech extraction provided the shortest intertwin delivery interval (Table 2).
Neonatal composite morbidity did not differ between the planned cesarean delivery and vaginal groups for first twins (4.9% compared with 3.3%, P=.44) (Table 3). Similar results for this outcome were obtained after multivariate analysis (adjusted odds ratio [aOR] 0.8, 95% confidence interval [CI] 0.2–2.5, P=.67) or exclusion of women who experienced pregnancy complications (0.0% compared with 3.5%, P=.63) (Table 3). Neonatal composite morbidity was significantly increased in the planned cesarean delivery compared with the planned vaginal group for second twins (14.8% compared with 4.9%, P < .001) (Table 4). Increased composite morbidity persisted in the planned cesarean delivery group even after adjustment for potential confounding variables (aOR 2.6, 95% CI 1.2–5.4, P=.014). After exclusion of women with pregnancy complications, factors included in the regression logistic models were maternal age, parity, fetal gender, gestational age, and birth weight. Neonatal composite morbidity for second twins did not differ between the two groups (5.0% compared with 4.7%, aOR 1.5, 95% CI 0.3–7.4, P=.63).
Although planned vaginal delivery was associated with more postpartum hemorrhages than planned cesarean delivery, rates of severe postpartum hemorrhages were similar between groups. Furthermore, maternal morbidity did not differ between planned cesarean and planned vaginal deliveries (4.9% compared with 7.0%, aOR 0.7, 95% CI 0.3–1.9, P=.52). Similar results were obtained after exclusion of pregnancy complications (5.0% compared with 6.4%, aOR 0.8, 95% CI 0.2–3.7, P=.81) (Table 5).
Planned vaginal delivery was associated with neither increased neonatal nor maternal adverse outcomes in comparison with planned cesarean delivery. In the first intent analysis, planned cesarean delivery was associated with increased neonatal composite morbidity for second twins. These differences were likely due to different population characteristics resulting from the selection of the eligible patients for the vaginal route at the daily obstetric staff meeting and not attributable to the planned route of delivery. Indeed, patients in the planned cesarean group had more pregnancy complications, delivered at an earlier gestational age, and had smaller newborns. However, after adjustment for these potential confounding variables, increased risk of poor neonatal outcome for second twins persisted in the planned cesarean delivery group. To eliminate residual confounders not controlled by the multivariate analysis, we excluded all the patients having experienced complications during their pregnancy. In this second analysis, in a low risk population, neonatal composite morbidity in second twins did not differ between groups, although some confounding factors might have persisted despite the multivariate analysis. Our results are in accordance with previous reports and meta-analyses, which did not show any significant differences associated with the mode of delivery in neonatal outcomes of second twins.2–9 Finally, although our study might not have been powered enough for evidencing differences in rare and severe adverse events related to the delivery route, the fact that no neonatal death occurred in 758 consecutive sets of twins in a 13-year period is reassuring.
We do believe absence of neonatal death and low rates of severe neonatal composite morbidity in the planned vaginal delivery group were likely related to patient selection and active management of second twin delivery for the following reasons: First, as suggested by the differences in maternal and fetal characteristics between the two groups, patients eligible for attempted vaginal delivery were carefully selected to reduce potential risks of adverse neonatal outcome associated with vaginal birth. Second, intertwin delivery interval was less than 5 minutes in the group of women who delivered both twins vaginally, shorter intervals being correlated with better neonatal outcomes.18–22 Short intertwin delivery intervals in our study can be explained by the nature of the obstetric interventions performed for second twin delivery. When the second twin was nonvertex, external version was contraindicated because this procedure has been shown to be associated with increased rates of cesarean delivery for second twin delivery.21,26 Immediate total breech extraction was then performed, this maneuver resulting in the shortest intertwin delivery intervals. Furthermore, the fact that two thirds of vertex second twins were internally rotated also might have contributed to the reduction of intertwin delivery intervals, because the mean elapsed time between births in this group was only 5.4±3.0 minutes. Third, we experienced only three cesarean deliveries for the second twin after vaginal birth of the first twin, an obstetric situation that is well-known for being associated with increased neonatal mortality and morbidity.13–15,20 Our rate of cesarean delivery for the second twin was 10- to 20-fold lower than previously reported.13,19,21 We acknowledge that internal version of the cephalic-presenting second twins might be an uncommon procedure in many countries. However, our results support the hypothesis that active management of second twin delivery, either by internal version or oxytocin infusion with maternal pushing efforts for cephalic presentations,23 is associated with low rates of cesarean delivery for second twin delivery.
The number of cesarean deliveries needed to prevent one neonatal death (incidence 0.1 to 0.5%) in the literature ranges from 264 to 1,451.17,28 These numbers were calculated from the data of large population-based studies.13,14,17 These reports suffer from the fact that information about second twin delivery management, such as intertwin delivery interval, second twin presentation, obstetric maneuvers, and even at times mode of delivery, are lacking or incomplete. Therefore, suggesting a protective effect of planned cesarean from these data might be inappropriate, knowing the effect of second twin delivery management on neonatal outcomes. Furthermore, the potential neonatal benefits of cesarean delivery in twin gestations have to be placed in the context of the short- and long-term risks associated with this mode of delivery. In singleton pregnancies, although absolute numbers are low, cesarean delivery in low-risk populations might triple the risk of maternal death29 and severe morbidity.30 Long-term effects of cesarean delivery are now being elucidated. During the pregnancy following cesarean delivery, women are at increased risk of placenta previa, placenta accreta, emergency cesarean delivery, and preterm birth.31 The number of cesarean deliveries needed to harm was three for one additional emergency cesarean delivery, 355 for one additional very preterm birth, and 1,536 for one additional placenta accreta.31 Cesarean delivery at the second gestation will expose women to even more morbidity events.32,33 Therefore, our results, along with the very recent data about short- and long-term morbidities29–33 associated with cesarean delivery, do not support systematic cesarean delivery for twin gestations in low-risk populations.
The results of this retrospective study must be interpreted with caution. The limitation of the cohort size, not powered to demonstrate a benefit of the vaginal birth for either neonates or mothers, must be acknowledged. However, our study provides detailed data on second twin delivery management, lacking in large population-based studies. Furthermore, since randomized trials may not be appropriate for evaluating complex phenomenons such as vaginal twin delivery,34 information regarding second twin delivery management might still result from in-hospital retrospective cohort studies.
In conclusion, our results suggest that, for twin gestations with a cephalic-presenting first twin, planned vaginal delivery after 35 weeks of gestation in selected patients remains a safe option in maternity units used to active management of second twin delivery. They should encourage obstetric staff members of university care centers to train obstetrics and gynecology residents in the maneuvers of assisted vaginal delivery before these procedures vanish, to the detriment of both mothers and their neonates.
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© 2008 The American College of Obstetricians and Gynecologists
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