Comparison of adverse maternal outcomes between early- and late-onset superimposed preeclampsia.

Superimposed preeclampsia (SIPE), defined as preeclampsia in individuals with chronic hypertension, is one of the most common complications, accounting for 13-40 % of pregnancies with chronic hypertension. However, there are limited data regarding maternal outcomes of early- and late-onset SIPE in individuals with chronic hypertension. We hypothesized that early-onset SIPE was associated with increased odds of adverse maternal outcomes compared to late-onset SIPE. Therefore, we aimed to compare adverse maternal outcomes between individuals with early-onset SIPE and those with late-onset SIPE. Study Design This was a retrospective cohort study of pregnant individuals with SIPE who delivered at 22 weeks' gestation or greater at an academic institution. Early-onset SIPE was defined as the onset of SIPE before 34 weeks' gestation. Late-onset SIPE was defined as the onset of SIPE at or after 34 weeks' gestation. Our primary outcome was a composite of eclampsia, HELLP syndrome, maternal death, placental abruption, pulmonary edema, SIPE with severe features, and thromboembolic disease. Maternal outcomes were compared between early-onset SIPE and late-onset SIPE. We used simple and multivariate logistic regression models to calculate crude and adjusted odds ratios (aOR) with 95% confidence intervals (95%CI). Results Of 311 individuals, 157 (50.5 %) had early-onset, 154 (49.5 %) had late-onset SIPE. There were significant differences in the proportions of obstetric complications, including the primary outcome, HELLP syndrome, SIPE with severe features, fetal growth restriction (FGR), and cesarean delivery between early- and late-onset SIPE. Compared to individuals with late-onset SIPE, those with early-onset SIPE had increased odds of the primary outcome (aOR 3.28; 95%CI 1.42-7.59), SIPE with severe features (aOR 2.72; 95%CI 1.25-5.90), FGR (aOR 6.07; 95%CI 3.25-11.36), and cesarean delivery (aOR 3.42; 95%CI 2.03-5.75). Conclusion In individuals with chronic hypertension, individuals with early-onset SIPE had higher odds of adverse maternal outcomes compared to those with late-onset SIPE.