Breastfeeding and Risk of Maternal Breast Carcinoma: A Systematic Review and Meta-analysis of Observational Studies

Background: Breast cancer is the most common malignancy and a leading cause of cancer death among women. Breastfeeding may protect against breast carcinoma by inducing hormonal changes, promoting mammary cell differentiation, and aiding carcinogen clearance. The consistency and magnitude of this association across populations remain unclear, warranting systematic evaluation. Objectives: To systematically assess the association between breastfeeding and maternal breast cancer risk, and to evaluate the impact of declining breastfeeding rates across diverse populations. Data collection and analysis: A systematic search of PubMed and the Cochrane Library identified observational studies (cohort and case-control). Two reviewers independently screened and extracted data on study design, sample size, breastfeeding duration, and effect estimates. Study quality was assessed using the Newcastle-Ottawa Scale, and pooled estimates were calculated with fixed-effects models. Main Results: In prospective cohort studies (RR; I² ≈ 35%), the pooled relative risk for ever versus never breastfeeding was 0.94 [95% CI 0.91–0.98], indicating a modest protective effect. In case-control studies (OR; I² ≈ 0%), the pooled odds ratio was 0.48 [95% CI 0.42–0.54], indicating significant risk reduction. Protective effects were consistently observed across NHS participants in US states and in Malaysian, North Indian, Nigerian, and Western-European populations. Conclusion: Breastfeeding is associated with a reduced risk of maternal breast carcinoma, with longer duration conferring greater protection. These findings reinforce the importance of public health initiatives promoting breastfeeding, formula marketing management, maternal support programs, and healthcare guidance to improve maternal health outcomes (SDG3) and advance gender equity (SDG5), despite sociocultural and workplace challenges.