Press Releases

1996 Releases

Breast Cancer Risk Linked to Infant Birthweight

For immediate release: December 05, 1996  

Boston, MA--Harvard School of Public Health researchers, in a study examining the prenatal influences on breast cancer, report a link between birthweight and future risk of breast cancer. Furthermore, the findings support the hypothesis that breast cancer may originate in utero, an hypothesis put forward in previous work by one of the co-authors, Dimitrios Trichopoulos, MD. The study, a case control study based on 2,151 women who participate in the Harvard Nurses Health Studies I and II, is reported in this week's Lancet.

"Our study shows a significant relationship between weight at birth and future breast cancer risk," comments Karin Michels, ScD, Harvard School of Public Health and lead author on the study. "But this should not lead women to strive for lower birthweight while pregnant." The study reports that women who weighed 2,500 grams or less (5 1/2 pounds) at birth had about half the risk of breast cancer than women who were 4,000 or more grams at birth (8.8 pounds).

Michels continues, "Our work is examining a variety of factors in early life that possibly play a role in the etiology of breast cancer. This study suggests that weight in relation to gestational age may be a critical factor in future breast cancer risk. We found that prematurity by itself was not a predictor of breast cancer." The authors suggest that the surge of maternal estrogen to the infant, which is correlated with higher birthweights, may be a factor that increases risk for the female fetus. Cells of mammary glands while in utero may be especially vulnerable to the effects of high estrogen levels or other pregnancy-related influences.

For further information, please contact:

Robin Herman
Office of Communications
Harvard School of Public Health
677 Huntington Avenue
Boston, MA 02115
Phone: 617-432-4752