Previous studies are inconclusive on the shape of the relationship between parity and cardiovascular disease, with few evaluating a range of cardiovascular outcomes. It is also unclear if any relationship between parity and cardiovascular disease is independent of breastfeeding. We examined the associations between parity and cardiovascular outcomes, including adjustment for breastfeeding duration.Methods
Data were from 8,609 Caucasian and African-American women, aged 45–64 years, participating in the Atherosclerosis Risk in Communities Study, a prospective epidemiological study with 24 years of follow-up. Cardiovascular outcomes [coronary heart disease (CHD); myocardial infarction (MI); heart failure; stroke] were identified through annual follow-up phone interviews and community-wide hospital surveillance and ascertained through 2012. At baseline and follow-up, parity and total duration of breastfeeding were self-reported. Cox proportional hazards regression models were used to estimate hazard ratios (HR) for the association between parity and cardiovascular outcomes, adjusting for baseline sociodemographic, clinical and lifestyle factors, and breastfeeding duration.Results
Women reported never being pregnant (6.0%), or having none (1.6%), 1–2 (36.0%), 3–4 (36.4%), or 5+ (19.7%) live births. During 26 years follow-up, there were the following numbers of incident events: 1,196 CHDs, 733 MIs, 635 strokes and 1321 heart failure events. Compared with women with 1–2 prior births, those with prior pregnancies and no live births had a higher risk of both incident CHD (HR=1.68, 95% CI:1.14–2.47) and heart failure (1.51, 1.07–2.14), after adjustment for baseline characteristics. Women with 5+births had a higher risk of incident CHD (1.30, 1.10–1.55) and hospitalised MI (1.40, 1.13–1.74), after adjustment for baseline characteristics and breastfeeding duration.Conclusions
In a diverse cohort of U.S. women, a history of 5+live births is associated with future risk of CHD, specifically, MI, independent of breastfeeding. Having a prior pregnancy and no live birth is associated with a greater risk of CHD and heart failure. Future studies should address whether the increased cardiovascular risk from multiparity arises from biological or lifestyle factors.