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 [52-58].
A higher birthweight doesn’t appear to be linked to higher estrogen levels in adulthood [59-61]. However, birthweight may be a marker of factors related to growth that are linked to breast cancer risk, such as adult height [60,62-63].
Other reasons behind the 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.