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

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.