Iatrogenic and spontaneous late preterm twins--which are at higher risk of neonatal complications?

OBJECTIVES: To evaluate data regarding neonatal mortality and short term morbidity among iatrogenic late preterm (ILP) and spontaneous late preterm (SLP) twin births, and to estimate whether medical interventions - induction of labor in this particular context, are associated with better or poorer outcomes.

MATERIAL AND METHODS: Retrospective analysis of 110 late preterm dichorionic twin pregnancies was performed basing on medical charts data. All twins were delivered in years 2005-2011 at the 1st Department of Obstetrics and Gynecology Medical University of Warsaw Late preterm twins, defined as those delivered between 34 + 0-36+ 6 weeks of gestation, were divided into spontaneous and iatrogenic preterm births. The primary outcomes of the study were various neonatal adverse events, including one of the following per pregnancy: admission to Neonatal Intensive Care Unit (NICU), respiratory disorders (RD) and pneumonia, intraventricular hemorrhage (IVH), sepsis, NEC and jaundice requiring phototherapy Mann-Whitney U-test and chi-squared test were used and logistic regression performed to calculate odds ratio, with p value < 0.05 considered significant.

RESULTS: There were 69 (62.7%) spontaneous and 41 (37.3%) iatrogenic late preterm twins. There were no differences in maternal characteristics, mode of delivery and newborns' Apgar scores. The mean birth weight did not differ significantly between the groups. There was one case of perinatal death of one twin in ILP group. Preeclampsia (31.7%) and IUGR (17%) were the most frequent indications for labor induction in ILR Women in the ILP group were administered steroid treatment for lung maturation more frequently than SLP group due to pregnancy complications (73.17% vs. 30.44%; p < 0.0001). Nevertheless, ILP twins were at higher risk of respiratory disorders (41.46% vs. 15.94%; p = 0.003--significant either with or without pneumonia) and NICU admission (31.71% vs. 14.49%; p = 0.032) than SLP twins. The only two independent factors influencing the occurrence of poor neonatal outcome were gestational age in weeks (OR 0.57; 95% Cl 0.34-0.94) and preeclampsia (OR 5.01; 95% CI 1.51-16.67). In the additional analysis of gestational age odds ratio, only the delivery at 34 weeks of gestation increased the incidence of adverse neonatal outcome almost five times (OR 4.94, 95% Cl: 1.64-14.88). The rate of cesarean delivery in the SLP was 81.61%, while in the ILP it reached 90.23% (p = 0.17).

CONCLUSIONS: Late prematurity in twin pregnancies is associated with higher risk of neonatal morbidity than in term twins. Iatrogenic late preterm birth increases the risk of NICU admission and respiratory disorders in neonates in comparison to spontaneous late preterm birth. Despite the fact that respiratory complications are generally mild and mostly temporary there is a need for careful evaluation of indications for delivery in that particular group.