Relationships between birth weight discordance and maternal and perinatal risks among twin pregnancies conceived following frozen embryo transfer.

This study investigates the association between intertwin birth weight discordance—defined as a ≥20% difference in birth weights—and adverse maternal and perinatal outcomes in twins conceived via frozen embryo transfer (FET), a form of assisted reproductive technology (ART). Analyzing 6,265 twin births from Shanghai Ninth People's Hospital (2007–2021), the study found that birth weight discordance in dichorionic twins was linked to a significantly increased risk of hypertensive disorders of pregnancy (HDP) in mothers and elevated neonatal mortality, with risks rising alongside the severity of discordance. For monochorionic twins, discordance was also associated with higher neonatal death risk. These findings suggest that pregnancies with intertwin birth weight discordance following ART may require enhanced antenatal surveillance to mitigate maternal and neonatal risks.