Impact of chorionicity on risk and timing of intrauterine fetal demise in twin pregnancies.
We sought to estimate the association between chorionicity and intrauterine fetal demise (IUFD) of one or both fetuses in twin pregnancies. In a retrospective cohort of twins undergoing anatomic survey, risk of IUFD in monochorionic and dichorionic twins was compared. The primary outcome was IUFD of one or both fetuses; secondary outcomes included nonanomalous fetal deaths. Of 2161 twin pregnancies meeting inclusion criteria, 86 had at least 1 IUFD and 32 experienced a double fetal loss. Monochorionic pregnancies had an increased risk of a single demise (adjusted odds ratio, 1.69; 95% confidence interval, 1.04-2.75) and a double demise (adjusted odds ratio, 2.11; 95% confidence interval, 1.02-4.37). Of all double demises, 70% occurred <24 weeks. Monochorionic twins carry an increased risk of fetal death compared to dichorionic twins. Double demise occurs primarily <24 weeks, regardless of chorionicity.