For new mothers, breastfeeding, even for a few months, is associated with a significant decrease in the risk for ovarian cancer years down the road, a review of studies has found.
The pooled analysis, in JAMA Oncology, included 13 studies with 9,973 ovarian cancer cases and 14,843 controls. After adjustment for age, race, oral contraceptive use and other factors, the researchers found that compared with never breastfeeding, any breastfeeding was associated with a 24 percent lower risk of ovarian cancer.
The lower risk was particularly strong for the most aggressive types of cancer, high-grade serous tumors.
The greater the duration of breastfeeding, the researchers found, the lower the risk for cancer. Nursing for one to three months was associated with an 18 percent lower risk, and for more than a year with a 34 percent lower risk. The association persisted for decades after breastfeeding ended — a 17 percent lower risk over the next 30 years or more.
A co-author, Dr. Naoko Sasamoto, a researcher at Brigham and Women’s Hospital in Boston, said that the reason for the association is not known.
“The risk of ovarian cancer is low, it is not a common disease,” she said. “But it has a high mortality, and there are few known modifiable risk factors. Our data shows that even a short duration of breastfeeding may be helpful.”