Optimal delivery timing for twin pregnancies: A population-based retrospective cohort study.

Abstract

The optimal timing of delivery for twin pregnancies remains controversial. This study examined the risks of adverse neonatal outcomes and neonatal deaths according to gestational age at delivery in order to determine the optimal gestational age of delivery for twin pregnancies. This is a retrospective study of twin pregnancies delivered between 34 and 40weeks of gestation from 1995 to 2000 in the United States. The primary outcomes evaluated were neonatal morbidity and mortality. The composite outcome of neonatal morbidity included the following variables: Apgar score lower than 7 at 5minutes, assisted ventilation <30minutes, assisted ventilation ≥30minutes, hyaline membrane disease, meconium aspiration syndrome, neonatal seizures, birth injury, anaemia, and congenital malformations. Logistic regressions were applied to calculate adjusted odds ratios of the adverse outcomes according to the gestational week at delivery, with either individual twins or twin pairs as the unit of analysis. A total of 466038 twins from 233019 pregnancies from the US National Center for Health Statistics matched the multiple birth data set included in the study. The composite neonatal morbidity and mortality risks declined from 34 to 38weeks of gestation and increased thereafter in both individual and pair twins stratified analyses. Amongst neonatal adverse outcomes, the risk of low Apgar score and hyaline membrane disease decreased progressively towards 38weeks of gestation, only to increase again towards 40weeks. The risk of meconium aspiration syndrome increased after 38weeks, in both individual and pair twins. There were no differences in the risk of birth injury and neonatal seizures when stratified by gestational age. The optimal timing for twin delivery appears to be at 38weeks of gestation, although individual maternal, foetal, and pregnancy characteristics should be considered when determining the best timing for delivery.