Superimposed versus de novo pre-eclampsia: Is there a difference?

Objective: To investigate whether pre-eclampsia is a single clinical entity or whether de novo pre-eclampsia and superimposed pre-eclampsia are distinct entities, with respect to baseline maternal characteristics, obstetrical complications, and perinatal outcomes. Methods: A retrospective cohort study comparing singleton pregnancies complicated with de novo pre-eclampsia (n = 10 979, 93%) and superimposed pre-eclampsia (n = 804, 7%). Maternal baseline characteristics, pregnancy and labor complications, and neonatal outcomes were evaluated in the univariate analysis. Multivariable logistic regression models were performed for the prediction of different pregnancy outcomes while controlling for confounders. Results: In the multivariate regression models controlling for confounders, superimposed pre-eclampsia was found to be a significant risk factor for placental dysfunction, a composite outcome composed of severe pre-eclampsia (rather than mild), placental abruption, oligohydramnios, and small-for-gestational-age neonate (odds ratio [OR] 2.23, 95% confidence interval [CI] 1.90–2.62, P < 0.001), preterm delivery (OR 2.79, 95% CI 2.39–3.26, P < 0.001), and perinatal mortality (OR 1.79, 95% CI 1.11–2.88, P = 0.02). Conclusion: De novo and superimposed pre-eclampsia demonstrated significant differences in most studied variables, suggesting that these may be two distinct clinical syndromes. In our population, superimposed pre-eclampsia was found to be significantly associated with adverse pregnancy outcomes such as placental dysfunction, preterm delivery, and perinatal mortality compared with de novo pre-eclampsia.