The effect of chorionicity on maternal and neonatal outcomes in triplet pregnancies.

Objective: Triplet gestations are associated with increased maternal, fetal, and neonatal complications particularly early and extreme preterm delivery. Identifying and interrupting the preterm delivery cascade could prevent the fetal, neonatal, and long-term childhood complications. The shared circulation and placental vascular anastomosis are responsible for the occurrence of twin-to-twin transfusion syndrome, selective fetal growth restriction as well as the higher risk of morbidity and mortality observed in mono and dichorionic compared to trichorionic triplet gestations. Thus, the aim of this study was to determine the effect of chorionicity on maternal, fetal, and neonatal outcomes of triplet pregnancies as it has not been fully ascertained.

Study Design: A retrospective population-based cohort study of 125 parturient with triplets' pregnancy who delivered at a single tertiary hospital.

Results: 98 trichorionic and 27 dichorionic gestations were included. Maternal demographic and obstetric characteristics as well as pregnancy and postpartum complications were similar in the two study groups. The median gestational age at delivery was lower among dichorionic than trichorionic triplet gestations (median 31 vs 33 weeks, p < 0.046). Early (<32 weeks) and extreme preterm delivery (<28 weeks) were more prevalent in the dichorionic than the trichorionic group (early - 56 % vs 34 %, p < 0.038; extreme - 33.3 % vs 8 %, p < 0.002). We found no difference in fetal or newborns' complications and characteristics between the groups. However, the rate of neonatal death was significantly higher in the dichorionic compared to trichorionic triplet gestations (22 % vs 7 %, p < 0.038). A multivariate logistic regression model to determine the variables that contribute to early preterm delivery in triplet gestations showed that women who experienced a past preterm delivery had an independently higher risk for early preterm delivery in the triplet gestation (adj. OR 5.91, 95 % CI 1.16-30.03). Neither maternal age nor chorionicity were found to be independent risk factors for early preterm delivery.

Conclusions: Dichorionic triplet gestations exhibit a higher rate of early (<32 weeks) and extreme (<28 weeks) preterm delivery and are more prone to neonatal death compared to trichorionic gestations. Past preterm delivery is an independent risk factor for early preterm delivery in a triplet gestation.