132: Delivery of monochorionic twins - Sub-analysis of the Twin Birth Study


      Conflicting data exist regarding outcomes of monochorionic (MC) twin deliveries. While some report higher risk of adverse neonatal outcomes, others do not. Yet, most of the data derives from retrospective studies, thus multiple confounders may have affected the results. Since the Twin Birth Study was a prospective, randomized trial, we aim to evaluate perinatal outcomes among MC twins in the TBS population.

      Study Design

      The TBS included women with a twin gestation at a gestational age of 34+0 to 38+6 weeks in which the first twin was in the vertex presentation at randomization. Women were then randomized to planned cesarean section (CS) or planned vaginal delivery (VD). For the purpose of this sub-analysis, we included all women with MC pregnancies. Women in the planned CS arm were compared to women in the planned VD arm. We also compared the neonatal outcomes of dichorionic twins (DC) with MC twins.


      Out of the 2588 women who were included in the original study, 670 (25.9%) had MC gestation, of which 324 (48.4%) were randomized to VD, and 346 (51.6%) to CS. No significant differences were found in maternal or obstetrical demographics between the groups, or in maternal outcomes. No differences were found in the subsequent analyses as well: twins A versus twins B, planned VD versus planned CS twin A, planned VD versus planned CS twin B and planned VD twin A versus twin B. In the planned CS arm, twins B had higher rate of Fetal/neonatal death or serious neonatal morbidity than twins A (3.2% vs. 1.2%, p=0.03), yet after exclusion of 2 neonatal deaths and 3 stillbirths, no differences were found in perinatal outcomes (Table 1).
      In the comparison of MC to DC twins, MC twins B were less likely to have a 5-minutes Apgar score<7 than DC twins B. Additionally, both MC twins A and B were less likely than DC twins A and B to have cord blood pH<7.0, and assisted ventilation (Table 2).


      These results provide reassurance regarding maternal and neonatal outcomes of deliveries of MC twins, and can be used in the consultation of women with MC twin pregnancy.
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