Impact of stage 1 hypertension before 20 gestational weeks on pregnancy outcomes in twin pregnancies: a retrospective cohort study

To explore the association between stage 1 hypertension before 20 weeks of gestation and twin pregnancy outcomes and to examine whether the association varies by prepregnancy BMI, conception mode, or chorionicity, we conducted a single-center, retrospective, hospital-based cohort study. All women who delivered twins between July 2014 and December 2020 were recruited. Logistic regression and linear regression models were used to identify associations. Among the 2069 included twin pregnancies, 1326 had normotension (< 130/80 mm Hg), and 743 had stage 1 hypertension (130–139/80–89 mm Hg). Compared with normotension, stage 1 hypertension was associated with higher risks of hypertension disorders of pregnancy (adjusted OR: 2.07, 95% CI: 1.62 ~ 2.64), gestational hypertension (adjusted OR: 3.99, 95% CI: 2.42 ~ 6.58), preeclampsia (adjusted OR: 1.71, 95% CI: 1.30 ~ 2.25), early preterm birth (adjusted OR: 1.58, 95%CI: 1.16 ~ 2.15), and small for gestational age (adjusted OR:1.45, 95%CI: 1.20 ~ 1.75). In particular, there were interaction effects between chorionicity and stage 1 hypertension on the risk of early preterm birth (P_interaction = 0.014). In conclusion, stage 1 hypertension before 20 weeks of gestation is associated with a higher risk of adverse outcomes in twin pregnancies, and the associations vary by prepregnancy BMI and chorionicity. Obstetricians should take this into careful consideration during prenatal care to mitigate the potential risks of twins.