730: Gestational age at delivery of twins and the risk of perinatal death: population cohort study

Abstract

Introduction: Twin pregnancy is associated with a threefold increase in perinatal mortality compared to singleton pregnancies. We aim to determine the week of gestation associated with the lowest risk of perinatal death in twins to inform clinicians regarding the optimum timing of delivery. Method(s): We performed a population based cohort study with twin pregnancies delivered at 34 weeks' gestation or greater from 1980- 2015 in Scotland using routinely collected maternity data. The primary outcome was perinatal mortality. We used generalised estimating equation modelling to determine the association between week of birth and perinatal death.We repeated the analysis with sex-discordant twins to represent dichorionic twins. The study was approved by the NHS Scotland Privacy Panel. Result(s): Results showed that in the cohort of 43 133 twins, infants born at 34 weeks had an increased odds of perinatal death compared to ongoing pregnancies (adjusted odds ratio [OR], 3.63, 95% CI 2.02 - 3.43) as did delivery at 35 and 36 weeks (adjusted OR 2.16, 95% CI 1.66-2.82 and adjusted OR 1.97, 95% CI 1.51- 2.58 respectively). Delivery from 38 weeks was associated with a trend towards a reduction in perinatal death compared to ongoing pregnancies but this was not significant (adj OR 0.96, 95% CI 0.64-1.56). In sex-discordant twins, delivery at 37-38 weeks was associated with a reduction in perinatal death compared to ongoing pregnancies (OR 0.48, 95% CI .29-0.80). Conclusion(s): Our data shows that gestation at delivery has a strong relationship with perinatal death with the highest risk of death in twin deliveries before 37 weeks gestation compared to ongoing twin pregnancies. After 37 weeks there is no evidence of a benefit of delivery in terms of perinatal death compared to ongoing pregnancies. In dichorionic twins delivery by 39 weeks appears to result in a reduction in death compared to ongoing pregnancies. To our knowledge this is the largest UK cohort study of twins and this information should be used when counselling women regarding timing of delivery of twin pregnancies. (Figure Presented).