Placental Component and Pregnancy Outcome in Singleton versus Twin Pregnancies Complicated by Preeclampsia

Objective: To compare placental histopathological lesions and pregnancy outcomes in singleton and twin pregnancies complicated by preeclampsia (PE). Methods: Maternal characteristics, neonatal outcomes, and placental histopathology reports of pregnancies complicated by PE between January 2008 and October 2016 were reviewed. Results were compared between singletons (singleton group) and dichorionic-diamniotic twins (twin group). Placental lesions were classified into maternal and fetal vascular supply lesions. Small for gestational age (SGA) was defined as birth weight ≤10th percentile. Composite adverse neonatal outcome was defined as one or more early neonatal complications. Results: Compared to the twin group (n = 67), the singleton group (n = 275) was characterized by lower maternal age (p = 0.003), higher gestational age (p < 0.001), higher rates of previous PE (p = 0.017), chronic hypertension (p = 0.036), and severe features (p < 0.001). Placentas from the singleton group were characterized by higher rates of maternal vascular malperfusion lesions (p < 0.001) and fetal vascular supply lesions (p = 0.002). Using multivariable regression analysis, composite maternal and fetal vascular malperfusion lesions were independently associated with singletons (aOR = 2.7, 95% CI = 1.2-7.8, p < 0.001, and aOR = 1.2, 95% CI = 1.2-5.6, p = 0.025, respectively). SGA was more common in the singleton group (p = 0.002). Neonatal outcome did not differ between the groups. Conclusion: Placentas from singleton pregnancies complicated by PE were characterized by higher rates of maternal and fetal vascular lesions compared to those from twin pregnancies, suggesting that different mechanisms participate in the development of PE in these two groups.