Twin pregnancies are risk factors for both early- and late-onset hypertensive disorders of pregnancy: the Japan Environment and Children's study.

This study investigated the associations of twin pregnancies with early-onset (EO)- and late-onset (LO)-hypertensive disorders of pregnancy (HDP). Totally, 86,717 pregnant women were included in a prospective birth cohort study. The associations of dichorionic diamniotic (DD)- and monochorionic diamniotic (MD)-twin pregnancies with EO-HDP (Diagnosed from 20 to <34 weeks of gestation) and LO-HDP (Diagnosed at ≥34 weeks of gestation) were analyzed using a multinomial logistic regression model. Compared with singleton pregnancies, both DD- and MD-twin pregnancies had significantly higher odds for EO- and LO-HDP. The adjusted odds ratios (aORs) for EO-HDP were 2.05 (95% confidence interval [Cl]: 1.51-2.78) in DD-twin pregnancies and 2.80 (95% Cl: 2.01-3.90) in MD-twin pregnancies, respectively. Also, the aORs for LO-HDP were 1.32 (95% CI: 1.03-1.69) in DD-twin pregnancies and 1.64 (95% Cl: 1.24-2.17) in MD-twin pregnancies, respectively. Although no statistically significant differences were observed, MD-twin pregnancies tended to have higher odds for both EO- and LO-onset HDP compared with DD-twin pregnancies. In conclusion, both DD- and MD-twin pregnancies are risk factors for the development of EO- and LO-HDP. We showed that both dichorionic diamniotic and monochorionic diamniotic twin pregnancies are risk factors for the development of early-onset and late-onset hypertensive disorders of pregnancy.