Lactation and the risk of epithelial ovarian cancer. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives

Int J Epidemiol. 1993 Apr;22(2):192-7. doi: 10.1093/ije/22.2.192.


The relationship between lactation and the development of epithelial ovarian cancer was assessed in data from seven countries that were collected for a multinational hospital-based case-control study conducted between 1979 and 1988. Three hundred and ninety-three cases of ovarian cancer were compared to 2565 controls matched on age, hospital, and year of interview. A non-significant reduction in risk with short-term lactation was observed but no further reduction in risk was seen with long-term lactation. The reduction in risk associated with months of lactation was not as great as the reduction with months of pregnancy, which may be a result of lactation being a less effective form of ovulation suppression than pregnancy. The short-term lactation that takes place in developed countries, may provide as great a reduction in risk as the long-term lactation practised in the developing countries included in this study.

Publication types

  • Comparative Study
  • Multicenter Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Breast Feeding
  • Case-Control Studies
  • Female
  • Humans
  • Lactation*
  • Ovarian Neoplasms / etiology
  • Ovarian Neoplasms / prevention & control*
  • Pregnancy
  • Risk
  • Time Factors