Association of body mass index with adverse pregnancy outcomes when stratified by cardiovascular health

Abstract Introduction High body mass index (BMI) is associated with adverse pregnancy outcomes, but it is not a direct measure of cardiovascular health (CVH) and misclassifies many. As CVH is a lead determinant of lifelong morbidity and mortality, we aimed to evaluate the association between BMI ≥30 and adverse pregnancy outcomes stratified by CVH. Methods Secondary analysis of the nuMoM2b multicenter cohort of nulliparas, excluding people with pregestational diabetes (GDM) and chronic hypertension. We used American Heart Association's Life's Simple 7 to assess CVH. Metrics included smoking, physical activity, healthy diet pattern, total cholesterol, and blood pressure. We omitted BMI given our objective, and we added triglycerides as these are a marker of CVH in pregnancy. We assigned 0 points for Poor category, 1 for Intermediate, and 2 for Ideal for each metric, with a maximum total score of 14. Total score was categorized as Poor (1–7), Intermediate (8–11), or Ideal (12–14). Outcomes included adverse perinatal outcomes previously linked to BMI. Association between exposures and outcomes was calculated via logistic regression. Results A total of 2381 participants were included, of which 445 (20.0%) had BMI ≥30, 134 (5.4%) had Poor CVH, 1733 (72.8%) had Intermediate CVH, and 514 (21.6%) had Ideal CVH. Overall, BMI ≥30 was associated with increased hypertensive disease of pregnancy (HDP, 38.7% vs. 19.6%; odds ratio OR, 2.6; 95% confidence interval CI, 2.1–3.2), severe preeclampsia (8.3 vs. 3.1%; OR, 2.8; 95% CI, 1.9–4.3), large for gestational age (LGA, 10.6% vs. 4.3%; OR, 2.6; 95% CI, 1.8–3.8), GDM (7.4% vs. 2.6%; OR, 3.0; 95% CI, 1.9–4.6), and cesarean birth (37.0% vs. 22.4%; OR, 2.0; 95% CI, 1.6–2.5). However, when stratified by CVH category, these associations were attenuated. In the Ideal CVH category, BMI ≥30 was only associated with LGA and GDM. Poor CVH was associated with an elevated risk of HDP regardless of BMI. Conclusion Relying on BMI alone to assess pregnancy risk appears to overestimate the risk of BMI ≥30 in those with otherwise Ideal CVH and underestimate in those with BMI 18.5–29.9 but Poor CVH. A more comprehensive assessment of CVH could result in a more accurate risk stratification.