Adverse pregnancy, birth, and infant outcomes in twins: effects of maternal fertility status and infant gender combinations; the Massachusetts Outcomes Study of Assisted Reproductive Technology

Risks of all maternal and most infant adverse outcomes were increased for subfertile and in vitro fertilization twins. Among all twins, the highest risks were for uterine bleeding and placental complications for the subfertile and in vitro fertilization groups, and neonatal and infant death in the subfertile group. These findings provide further evidence supporting single embryo transfer and more cautious use of ovulation induction.