Studies show women with a higher birthweight (a woman’s weight at her birth) appear to have an increased risk of breast cancer (especially before menopause) [142,331-334].
A higher birthweight does not appear to be linked to higher estrogen levels in adulthood [335-337].
However, birthweight may be a marker of factors related to growth (such as adult height) that affect breast cancer risk [336,338-339]. Other reasons behind a link between birthweight and breast cancer risk are under study.
Learn about other early life exposures and breast cancer risk.
Breast Cancer 101 - Risk Factors
Facts for Life: Breast Cancer & Risk
Research Fast Facts: Breast Cancer Inequities