OBJECTIVES: We sought to document the pregnancy and neurodevelopmental outcome in monochorionic diamniotic twin pregnancies and to identify risk factors for death and impairment. STUDY DESIGN: We conducted a prospective cohort study of 136 monochorionic twins followed up from the first trimester until infancy. RESULTS: A total of 122 (90%) pregnancies resulted in 2 survivors, 6 (4%) in 1 survivor and 8 (6%) in no survivor. In all, 230 (92%) of 250 surviving infants were assessed at a mean age of 24 months. Neurodevelopmental impairment was present in 22 (10%) infants. Death or impairment of 1 or both infants occurred in 28 (22%) of 126 pregnancies. Twin-to-twin transfusion syndrome and assisted conception increased the risk of both death and impairment, whereas early-onset discordant growth only increased the risk of death. CONCLUSION: The mortality in this prospective series was 8% and neurodevelopmental impairment occurred in 10% of infants.
