The Effect of Breastfeeding Duration and Parity on the Risk of Epithelial Ovarian Cancer: A Systematic Review and Meta-analysis

J Prev Med Public Health. 2016 Nov;49(6):349-366. doi: 10.3961/jpmph.16.066. Epub 2016 Sep 8.


Objectives: We conducted a systematic review and meta-analysis to summarize current evidence regarding the association of parity and duration of breastfeeding with the risk of epithelial ovarian cancer (EOC).

Methods: A systematic search of relevant studies published by December 31, 2015 was performed in PubMed and EMBASE. A random-effect model was used to obtain the summary relative risks (RRs) and 95% confidence intervals (CIs).

Results: Thirty-two studies had parity categories of 1, 2, and ≥3. The summary RRs for EOC were 0.72 (95% CI, 0.65 to 0.79), 0.57 (95% CI, 0.49 to 0.65), and 0.46 (95% CI, 0.41 to 0.52), respectively. Small to moderate heterogeneity was observed for one birth (p<0.01; Q=59.46; I2=47.9%). Fifteen studies had breastfeeding categories of <6 months, 6-12 months, and >13 months. The summary RRs were 0.79 (95% CI, 0.72 to 0.87), 0.72 (95% CI, 0.64 to 0.81), and 0.67 (95% CI, 0.56 to 0.79), respectively. Only small heterogeneity was observed for <6 months of breastfeeding (p=0.17; Q=18.79, I2=25.5%). Compared to nulliparous women with no history of breastfeeding, the joint effects of two births and <6 months of breastfeeding resulted in a 0.5-fold reduced risk for EOC.

Conclusions: The first birth and breastfeeding for <6 months were associated with significant reductions in EOC risk.

Keywords: Breast feeding; Meta-analysis; Ovarian neoplasms; Parity; Reproduction; Risk factors.

Publication types

  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • BRCA1 Protein / genetics
  • BRCA2 Protein / genetics
  • Breast Feeding*
  • Carcinoma, Ovarian Epithelial
  • Databases, Factual
  • Female
  • Humans
  • Mutation
  • Neoplasms, Glandular and Epithelial / etiology*
  • Odds Ratio
  • Ovarian Neoplasms / etiology*
  • Parity
  • Risk
  • Time Factors


  • BRCA1 Protein
  • BRCA2 Protein