Impact of chorionicity on risk and timing of intrauterine fetal demise in twin pregnancies

Objective: We sought to estimate the association between chorionicity and intrauterine fetal demise (IUFD) of one or both fetuses in twin pregnancies. Study Design: 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. Results: 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. Conclusion: Monochorionic twins carry an increased risk of fetal death compared to dichorionic twins. Double demise occurs primarily <24 weeks, regardless of chorionicity.