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San Francisco, C.A. — Gaining more than 50 pounds during pregnancy, and not losing the excess weight post-pregnancy, could triple a woman's risk of developing breast cancer after menopause, according to a study conducted by researchers at Lombardi Cancer Center in Washington, DC, and in Finland. Pregnancy weight gain of 40 pounds increased breast cancer risk by 40%. The findings are to be presented April 9 at the American Association for Cancer Research (AACR) annual meeting in San Francisco.
Pregnancy weight gain has been linked in previous studies to increased estrogen levels, which in turn are believed to increase breast cancer risk, researchers said. The researchers' findings are based on the study of more than 27,000 breast cancer patients in Finland, identified through a national cancer registry. Information about breast cancer diagnosis and pregnancy weight gain were obtained from a national cancer registry, maternity center registries and from a questionnaire completed by the study participants.
"Significant weight gain during pregnancy may cause changes in breast tissue that increase susceptibility to breast cancer in later life-roughly equivalent to the risk of postmenopausal obesity," said Leena Hilakivi-Clarke, PhD, one of the study's investigators and associate professor of oncology at the Lombardi Cancer Center at Georgetown University Medical Center. "Women who retain the added pounds after pregnancy are at the greatest risk."
Weight gain during pregnancy appeared to increase breast cancer risk only after menopause, Hilakivi-Clarke said, adding that each 1 kg (2.2 pounds) increase in pregnancy weight increased breast cancer risk by 3.9%, when adjusted for body mass index before pregnancy.
Weight gain of 25 to 35 pounds is normal in pregnancy and not associated with an increase in risk for either premenopausal or postmenopausal breast cancer, Hilakivi-Clarke noted.
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