Risk Factors for Early- and Late-Onset Superimposed Preeclampsia

Risk factors of early- and late-onset preeclampsia among pregnant individuals with chronic hypertension are not well described in the literature. We hypothesized that early- and late-onset superimposed preeclampsia (SIPE) have different risk factors. Therefore, we aimed to examine the risk factors of early- and late-onset SIPE among individuals with chronic hypertension.

This was a retrospective case-control study of pregnant individuals with chronic hypertension who delivered at 22 weeks' gestation or greater at an academic institution. Early-onset SIPE was defined as SIPE diagnosed before 34 weeks' gestation. To identify risk factors, we compared individuals' characteristics between individuals who developed early- and late-onset SIPE and those who did not. We then compared characteristics between individuals who developed early-onset SIPE and late-onset SIPE. Characteristics with p-values of less than 0.05 by bivariable variables were analyzed by simple and multivariable logistic regression models to calculate crude and adjusted odds ratios (aOR) and 95% confidence intervals (95% CI). Missing values were imputed with multiple imputation.

Of 839 individuals, 156 (18.6%) had early-onset, 154 (18.4%) had late-onset SIPE and 529 (63.1%) did not have SIPE. The multivariate logistic regression model showed that serum creatinine ≥ 0.7 mg/dL compared to less than 0.7 mg/dL (aOR: 2.89 [95% CI: 1.63-5.13]), increase of creatinine (1.33 [1.16-1.53]), nulliparity compared to multiparity (1.77 [1.21-2.60]), and pregestational diabetes (1.70 [1.11-2.62]) were risk factors for early-onset SIPE. The multivariate logistic regression model showed that nulliparity compared to multiparity (1.53 [1.05-2.22]) and pregestational diabetes (1.74 [1.14-2.64]) was a risk factor for late-onset SIPE. Serum creatinine ≥ 0.7 mg/dL (2.90 [1.36-6.15]) and increase of creatinine (1.33 [1.10-1.60]) were significantly associated with early-onset SIPE compared to late-onset SIPE.

Kidney dysfunction seemed to be associated with the pathophysiology of early-onset SIPE. Nulliparity and pregestational diabetes were common risk factors for both early- and late-onset SIPE.

· Serum creatinine level was positively associated with early-onset superimposed preeclampsia (SIPE).. · Pregestational diabetes and nulliparity were associated with both early- and late-onset SIPE.. · The identification of risk factors may provide an opportunity to decrease the rates of SIPE..