查看文章

Although childbearing is known to protect against breast cancer, whether or not breastfeeding contributes to this protective effect is unclear.

Individual data from 47 epidemiological studies in 30 countries that included information on breastfeeding patterns and other aspects of childbearing were collected, checked, and analysed centrally, for 50 302 women with invasive breast cancer and 96 973 controls. Estimates of the relative risk for breast cancer associated with breastfeeding in parous women were obtained after stratification by fine divisions of age, parity, and women's ages when their first child was born, as well as by study and menopausal status.

Women with breast cancer had, on average, fewer births than did controls (2·2 vs 2·6). Furthermore, fewer parous women with cancer than parous controls had ever breastfed (71%vs 79%), and their average lifetime duration …