To evaluate the relationship between maternal body mass index (BMI) at delivery and rates of early-onset and late-onset hypertensive disorders of pregnancy.
We performed a population-based, retrospective cohort study using U.S. Vital Statistics period-linked birth and infant death certificates from 2014 to 2017. Women who delivered a nonanomalous singleton live neonate from 24 to 41 completed weeks of gestation were included. We excluded women with chronic hypertension and those with BMIs less than 18.5. The primary exposure was maternal BMI, defined as nonobese (BMI 18.5–29.9; referent group), class 1 obesity (BMI 30.0–34.9), class 2 obesity (BMI 35.0–39.9), and class 3 obesity (BMI 40.0 or greater). The primary outcome was delivery with hypertensive disorders of pregnancy (gestational hypertension, preeclampsia, or eclampsia) at less than 34 weeks of gestation or at 34 weeks or more. Multivariable Poisson regression was used to estimate relate risk and adjust for confounding variables. Results are presented as adjusted relative risk (aRR) and 95% CIs.
Of the 15.8 million women with live births during the study period, 14.0 million (88.6%) met inclusion criteria, and 825,722 (5.9%) had hypertensive disorders of pregnancy. The risk of early-onset hypertensive disorders of pregnancy was significantly higher in women with class 1 obesity (aRR 1.13; 95% CI 1.10–1.16), class 2 obesity (aRR 1.57; 95% CI 1.53–1.62), and class 3 obesity (aRR 2.18; 95% CI 2.12–2.24), compared with nonobese women. The risk of late-onset hypertensive disorders of pregnancy was also significantly increased in women with class 1 obesity (aRR 1.71; 95% CI 1.70–1.73), class 2 obesity (aRR 2.60; 95% CI 2.58–2.62), and class 3 obesity (aRR 3.93; 95% CI 3.91–3.96) compared with nonobese women.
Compared with nonobese women, the risk of early-onset and late-onset hypertensive disorders of pregnancy is significantly and progressively increased among women with increased class of obesity.