Confounders
We adjusted for several confounders including maternal age (<15, 15-19, 20-24, 25-29 [reference], 30-34, 35-39, and ≥40 years), education (below high school, up to high school, college, and beyond college educated), race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, or other race), maternal smoking (non-smoker [reference], smoked before pregnancy only, and smoked before and during pregnancy), single marital status, pre-pregnancy body-mass index (BMI in kg/m2; underweight [<18.5], normal [18.5-24.9], overweight [25.0-29.9], obese [30.0-34.9], and morbidly obese [≥35.0]), and pregestational diabetes. We also adjusted for year of delivery to address potential temporal changes in the prevalence of chronic hypertension and maternal mortality.