Body Mass Index, Adverse Pregnancy Outcomes, and Cardiovascular Disease Risk

Abstract

BACKGROUND: Obesity is a well-established risk factor for both adverse pregnancy outcomes (APOs) and cardiovascular disease (CVD). However, it is not known whether APOs are mediators or markers of the obesity-CVD relationship. This study examined the association between body mass index, APOs, and postpartum CVD risk factors. METHODS: The sample included adults from the nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be) Heart Health Study who were enrolled in their first trimester (6 weeks–13 weeks 6 days gestation) from 8 United States sites. Participants had a follow-up visit at 3.7 years postpartum. APOs, which included hypertensive disorders of pregnancy, preterm birth, small-for-gestational-age birth, and gestational diabetes, were centrally adjudicated. Mediation analyses estimated the association between early pregnancy body mass index and postpartum CVD risk factors (hypertension, hyperlipidemia, and diabetes) and the proportion mediated by each APO adjusted for demographics and baseline health behaviors, psychosocial stressors, and CVD risk factor levels. RESULTS: Among 4216 participants enrolled, mean±SD maternal age was 27±6 years. Early pregnancy prevalence of overweight was 25%, and obesity was 22%. Hypertensive disorders of pregnancy occurred in 15%, preterm birth in 8%, small-for-gestational-age birth in 11%, and gestational diabetes in 4%. Early pregnancy obesity, compared with normal body mass index, was associated with significantly higher incidence of postpartum hypertension (adjusted odds ratio, 1.14 [95% CI, 1.10–1.18]), hyperlipidemia (1.11 [95% CI, 1.08–1.14]), and diabetes (1.03 [95% CI, 1.01–1.04]) even after adjustment for baseline CVD risk factor levels. APOs were associated with higher incidence of postpartum hypertension (1.97 [95% CI, 1.61–2.40]) and hyperlipidemia (1.31 [95% CI, 1.03–1.67]). Hypertensive disorders of pregnancy mediated a small proportion of the association between obesity and incident hypertension (13% [11%–15%]) and did not mediate associations with incident hyperlipidemia or diabetes. There was no significant mediation by preterm birth or small-for-gestational-age birth. CONCLUSIONS: There was heterogeneity across APO subtypes in their association with postpartum CVD risk factors and mediation of the association between early pregnancy obesity and postpartum CVD risk factors. However, only a small or nonsignificant proportion of the association between obesity and CVD risk factors was mediated by any of the APOs, suggesting APOs are a marker of prepregnancy CVD risk and not a predominant cause of postpartum CVD risk.

Adverse Pregnancy Outcomes and Predicted 30-Year Risk of Maternal Cardiovascular Disease 2–7 Years After Delivery

“…In a recent analysis using data from this cohort, Khan et al 25 noted that adverse pregnancy outcomes mediated only a small amount of the relationship between early-pregnancy obesity and atherosclerotic CVD risk factors 2–7 years after delivery. Further understanding of pathophysiologic mechanisms may help address whether adverse pregnancy outcomes reflect latent risk for atherosclerotic CVD that is unmasked in pregnancy or whether adverse pregnancy outcomes themselves are causal risk factors for future atherosclerotic CVD, which may guide counseling and interventions.…”

“…Baseline covariates (at cohort enrollment) included the following sociodemographic and clinical characteristics: maternal age (continuous), prepregnancy smoking status (yes or no), health insurance status (private vs public), first-trimester body mass index (BMI, calculated as weight in kilograms divided by height in meters squared; continuous), neighborhood-level social determinants of health assessed by the Area Deprivation Index (tertiles from the least deprivation [best, tertile 1] to the most deprivation [worst, tertile 3]), 23 and time from delivery to postpartum atherosclerotic CVD risk assessment (continuous). These covariates were selected for inclusion in the multivariable models from a directed acyclic graph informed by theoretical paradigms of the relationship among adverse pregnancy outcomes, 24 cardiometabolic risk factors, 25 social determinants of health, 8 and atherosclerotic CVD (Appendix 1, available online at http://links.lww.com/AOG/D632). We did not adjust for cardiometabolic risk factors (ie, hypertension, diabetes, obesity, elevated lipids) because these factors were considered to be on the causal pathway between adverse pregnancy outcomes and atherosclerotic CVD and were predictors included in the calculation of the risk prediction outcome measure.…”

Postpartum weight retention and the early evolution of cardiovascular risk over the first 5 years after pregnancy

“…There is currently considerable interest in the intersection of pregnancy, body weight and future risk of cardiovascular disease (CVD) [1][2][3]. Indeed, maternal weight gain over the 9-months of gestation is an anticipated feature of normal pregnancy.…”