Multifetal gestation is a known risk factor for pre-eclampsia, but the degree of increased risk for eclampsia has not been quantified. Our objectives were to: 1) compare rates of eclampsia in singleton versus twin and higher order multifetal gestations and 2) investigate whether eclampsia in multifetal gestations is associated with higher maternal morbidity. We conducted a cross-sectional study using the US Vital Statistics birth certificate data to identify cases of eclampsia in live-born singleton, twin and higher order multifetal gestations between 2014 and 2018. We excluded subjects with fetal anomalies, gestational age < 24 or > 42 weeks, or missing maternal comorbidity or outcome data. Multivariable Poisson regression with robust error variance was used to compare rates of eclampsia between pregnancies with singleton, twin, and higher order multifetal gestations. Similarly, rates of composite adverse maternal outcome (CMAO; includes any of the following: blood transfusion, ICU admission, unplanned cesarean hysterectomy, and uterine rupture) were compared between groups among pregnancies with eclampsia. Among the 18.8 million pregnancies identified that met inclusion criteria, the rates of eclampsia increased with increasing degree of multiple gestation (Table 1). Twin pregnancies were more than twice as likely (aRR 2.55, 95% CI 2.47-2.63) to be affected by eclampsia compared to singleton gestations, while triplets and higher order multiples were nearly four times as likely to be affected by eclampsia (RR 3.71, 95% CI 3.20-4.31). Among those with eclampsia, CMAO was higher in multifetal gestations compared to singletons (aRR 1.38, 95% CI 1.16-1.64; Table 2). Multifetal gestations are at increased risk of eclampsia compared to singletons, and risk is increased in higher order pregnancies. Among pregnancies affected by eclampsia, multifetal gestation is associated with higher rates of adverse maternal outcomes compared to singletons.View Large Image Figure ViewerDownload Hi-res image Download (PPT)