A longer duration of breastfeeding is associated with a lower risk for endometriosis in the mother, according to a study in The BMJ.
Researchers studied 72,000 participants from the Nurses' Health Study II who reported at least one pregnancy. Over 20 years' follow-up, 5% had confirmed endometriosis.
For every 3 additional months of total breastfeeding (up to 45 months), the risk for endometriosis fell by 3%. Women who breast-fed exclusively for 18 months or more across their reproductive lives had a 27% lower risk than women who did not breast-feed exclusively (199 vs. 413 cases per 100,000 person-years). The association was influenced by longer duration of postpartum amenorrhoea.
The authors note that breast-feeding promotes circulating oxytocin and prolactin and inhibits circulating gonadotropins. They conclude: "Given the chronic and incurable nature of endometriosis, breast feeding should be further investigated as an important modifiable behaviour to mitigate risk for pregnant women."