INTRODUCTION: Prepregnancy obesity (body mass index [BMI]≥30) has been consistently associated with maternal morbidity. The rate of morbid obesity (BMI≥40) appears to be increasing. This study investigated whether morbid obesity was associated with severe maternal morbidity in a population cohort. METHODS: Internal review board exemption was obtained. We identified 197,822 patients using the birth-certificate-based New York Statewide Perinatal Data System from 2010 to 2020. Women were divided into two categories, those with prepregnancy BMI <40 and those with prepregnancy BMI ≥40 (morbid obesity). The risk of severe maternal morbidity (maternal transfusion, intensive care unit admission, unplanned hysterectomy, and unplanned reoperation) was compared. We also compared the risk of cesarean delivery, hypertensive disorders of pregnancy, and gestational diabetes. Chi-square and t tests were used to compare categorical and continuous variables respectively. RESULTS: We identified 197,822 deliveries, of which 13,120 (6.63%) were complicated by maternal morbid obesity. Morbidly obese women had a significantly higher risk of severe morbidity (RR, 1.16; 95% CI, 1.003–1.33). The risk of intensive care unit admission was significantly increased (RR, 1.84; 95% CI, 1.35–2.53), but blood transfusion, unplanned hysterectomy, and unplanned reoperation were unchanged. CONCLUSION: Morbid obesity was associated with increased severe maternal morbidity specifically due to maternal intensive care unit admission. This may indicate a higher risk of severe medical complications and likely represents a higher risk of maternal mortality. [ABSTRACT FROM AUTHOR]