Breastfeeding Significantly Decreases Ovarian Cancer Risk, Including The Deadliest Form of the Disease

Women who breastfeed may be reducing their risk for ovarian cancer—including the most deadly type of ovarian cancer, researchers have found.

“Breastfeeding has been associated with a reduced risk of epithelial ovarian cancer in multiple studies, but others showed no association. Whether risk reduction extends beyond that provided by pregnancy alone or differs by histotype is unclear. Furthermore, the observed associations between duration and timing of breastfeeding with ovarian cancer risk have been inconsistent,” the researchers posited in their paper.

The researchers analyzed parous women with ovarian cancer and controls from 13 case-control studies that were part of the Ovarian Cancer Association Consortium. Data were gathered between November 1989 and December 2009 and assessed between September 2017 and July 2019. Exposures were data on breastfeeding history, which included duration per child breastfed, age at first and last breastfeeding, and years since last breastfeeding. The primary outcome was a diagnosis of epithelial ovarian cancer.

Breastfeeding Reduces Cancer Risk

Final analysis included 9,973 women with ovarian cancer (mean [SD] age, 57.4 [11.1] years) and 13,843 controls (mean [SD] age, 56.4 [11.7] years). Women who breastfed had a 24% lower risk of invasive ovarian cancer (odds ratio [OR]=0.76; 95% confidence interval [CI], 0.71 to 0.80). A correlation independent of parity was observed between ever breastfeeding and a reduced risk of all invasive ovarian cancers—notably high-grade serous and endometrioid cancers. The authors reported that for one episode, mean duration of one to three months correlated with an 18% lower risk (OR=0.82; 95% CI, 0.76 to 0.88); the risk was even lower for women who did so for 12 or more months (34%; OR=0.66; 95% CI, 0.58 to 0.750. “More recent breastfeeding was associated with a reduction in risk (OR, 0.56; 95% CI, 0.47-0.66 for <10 years) that persisted for decades (OR, 0.83; 95% CI, 0.77-0.90 for ≥30 years; P for trend = .02),” the researchers added.

The study was published in JAMA Oncology.

The study authors concluded that, “Breastfeeding is associated with a significant decrease in risk of ovarian cancer overall and for the high-grade serous subtype, the most lethal type of ovarian cancer. The findings suggest that breastfeeding is a potentially modifiable factor that may lower risk of ovarian cancer independent of pregnancy alone.”