This systematic review aims to explore the association between birth weight and the risk of developing breast cancer later in life. We conducted a comprehensive search of relevant studies published up to August 2024 across multiple databases, including PubMed, Scopus, and Web of Science. Studies were included if they examined the relationship between birth weight and breast cancer risk, provided clear measurements of birth weight, and presented relative risks, odds ratios, or hazard ratios with corresponding confidence intervals. Data extraction and quality assessment were performed independently by two reviewers. A total of 25 studies met the inclusion criteria, encompassing diverse populations and study designs. The findings indicate a potential correlation between higher birth weights and an increased risk of breast cancer in adulthood. The pooled analysis suggested a modest but statistically significant association, with a higher birth weight being linked to a 15% increased risk of breast cancer (RR 1.15, 95% CI: 1.05-1.26). Subgroup analyses highlighted variations in risk based on menopausal status, with premenopausal women exhibiting a stronger association compared to postmenopausal women. This systematic review suggests that higher birth weight may be associated with an elevated risk of breast cancer. These findings underscore the importance of considering early life factors in the etiology of breast cancer. Further research is warranted to elucidate the underlying mechanisms and to explore potential preventive strategies targeting this risk factor.

Birth weight, Breast cancer, Risk factors

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