Duration of Lactation and Risk Factors for Maternal Cardiovascular Disease

To examine dose-response relationships between the cumulative number of months women lactated and postmenopausal risk factors for cardiovascular disease. We examined data from 139,681 postmenopausal women (median age 63 years) who reported at least one live birth on enrolling in the Women's Health Initiative observational study or controlled trials. Multivariable models were used to control for sociodemographic (age, parity, race, education, income, age at menopause), lifestyle, and family history variables when examining the effect of duration of lactation on risk factors for cardiovascular disease, including obesity (body mass index [BMI] at or above 30), hypertension, self-reported diabetes, hyperlipidemia, and prevalent and incident cardiovascular disease. Dose-response relationships were seen; in fully adjusted models, women who reported a lifetime history of more than 12 months of lactation were less likely to have hypertension (odds ratio [OR] 0.88, P