Risk of late-preterm stillbirth and neonatal morbidity for monochorionic and dichorionic twins

OBJECTIVE: The purpose of this study was to determine the prospective risk of intrauterine fetal death (IUFD) at >= 34 weeks' gestation for monochorionic and dichorionic twins receiving intensive antenatal fetal surveillance. The secondary objective was to calculate the incidence of prematurity-related neonatal morbidity/mortality rates that have been stratified by gestational week and chorionicity. STUDY DESIGN: A retrospective cohort study of all twins at >= 34 weeks' gestation who were delivered at the Medical University of South Carolina (1987-2010) was performed. Twins were cared for in a long-standing Twin Clinic with standardized treatment and surveillance protocols and supervised by a consistent Maternal-Fetal Medicine specialist. Gestational age-especific fetal/neonatal mortality rates and composite neonatal morbidity rates were compared by chorionicity. A generalized linear mixed model was used to identify variables that were associated with increased composite neonatal morbidity. RESULTS: Among 768 twin gestations (601 dichorionic and 167 monochorionic), only 1 dichorionic IUFD occurred. The prospective risk of IUFD at >= 34 weeks' gestation was 0.17% for dichorionic twins and 0% for monochorionic twins. Composite neonatal morbidity decreased with each gestational week (P < .0001). Morbidity was increased by white race, gestational diabetes mellitus, and elective indication for delivery. The nadir of composite neonatal morbidity occurred at 36/0-36/6 weeks' gestation for monochorionic twins and 37/0-37/6 weeks' gestation for dichorionic twins. CONCLUSION: Our data do not support concern for an increased risk of stillbirth in uncomplicated intensively monitored monochorionic twins at >= 34 weeks' gestation. However, our data do show significantly increased rates of neonatal morbidity in late preterm monochorionic twins that cannot be justified by a corresponding reduction in the risk of stillbirth. We believe that our data support delivery of uncomplicated monochorionic twins at 37 weeks' gestation.