Breastfeeding Is Associated With a Reduced Maternal Cardiovascular Risk: Systematic Review and Meta-Analysis Involving Data From 8 Studies and 1 192 700 Parous Women

Background: Breastfeeding has been robustly linked to reduced maternal risk of breast cancer, ovarian cancer, and type-2 diabetes mellitus. We herein systematically reviewed the published evidence on the association of breastfeeding with maternal risk of cardiovascular disease (CVD) outcomes.
Methods and Results: Our systematic search of PubMed and Web of Science of articles published up to 16 April 2021 identified eight relevant prospective studies involving 1,192,700 parous women (weighted mean age: 51.3 years at study entry, 24.6 years at first birth; weighted mean number of births: 2.3). 982,566 women (82%) reported having ever breastfed (weighted mean lifetime duration of breastfeeding: 15.6 months). Over a weighted median follow-up of 10.3 years, 54,226 CVD, 26,913 coronary heart disease, 30,843 stroke, and 10,766 fatal CVD events were recorded. In a random-effects meta-analysis, the pooled multivariable adjusted hazard ratios comparing parous women who ever to those who never breastfed were: 0.89 for CVD (95% CI: 0.83-0.95; I2=79.4%); 0.86 for coronary heart disease (0.78-0.95; I2=79.7%); 0.88 for stroke (0.79-0.99; I2=79.6%); and 0.83 for fatal CVD (0.76-0.92; I2=47.7%). The quality of the evidence using GRADE ranged from very low to moderate, which was mainly driven by high between-studies heterogeneity. Strengths of associations did not differ by mean age at study entry, median follow-up duration, mean parity, level of adjustment, study quality, or geographical region. A progressive risk reduction of all CVD outcomes with lifetime durations of breastfeeding from 0 up to 12 months was found, with some uncertainty about shapes of associations for longer durations.
Conclusions: Breastfeeding was associated with reduced maternal risk of CVD outcomes.