Studies show women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer (especially before menopause) [49-53].
A higher birthweight does not appear to be linked to higher estrogen levels in adulthood [54-56]. However, birthweight may be a marker of factors related to growth (such as adult height) that affect breast cancer risk [55,57-58].
Other reasons behind a link between birthweight and breast cancer risk are under study.
Learn about other early life exposures and breast cancer risk.
For a summary of research studies on birthweight and breast cancer risk, visit the Breast Cancer Research Studies section.
Breast Cancer 101 - Risk Factors
Facts for Life: Breast Cancer & Risk
Research Fast Facts: Breast Cancer Inequities