Below is a selection of studies exploring the impact of breastfeeding on ovarian cancer risk. For more details on this, see our maternal health meta-analyses research section.
Breastfeeding factors and risk of epithelial ovarian cancer
This US study examined the association between breastfeeding factors and epithelial ovarian cancer (EOC). It found that compared to never breastfeeding, breastfeeding any offspring was associated with a 30% reduction in EOC risk. That association lasted more than 30 years and was dose-respondent, and an earlier age at first breastfeeding was further associated with increased protection.
Modugno, F, Goughnour, S, Wallack, D, et al, (2019). Breastfeeding factors and risk of epithelial ovarian cancer. Gynecologic Oncology 2019 January 25
The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015
This study explored the fraction of cancer cases attributable to modifiable risk factors in the UK, finding that nearly four in ten (37.7%) cancer cases in 2015 in the UK were attributable to known risk factors. Researchers identified not breastfeeding as one such risk factor; amongst women, not breastfeeding was attributed to 2,582 cancer cases in 2015.
Brown, K, et al, (2018). The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015, British Journal of Cancer, doi:10.1038/s41416-018-0029-6.
The Effect of Breastfeeding Duration and Parity on the Risk of Epithelial Ovarian Cancer: A Systematic Review and Meta-analysis
This review of studies exploring the association of parity and duration of breastfeeding with the risk of epithelial ovarian cancer (EOC) found that the first birth and breastfeeding for less than six months were associated with significant reductions in EOC risk.
Sung, HK, et al (2016). The Effect of Breastfeeding Duration and Parity on the Risk of Epithelial Ovarian Cancer: A Systematic Review and Meta-analysis, Journal of Preventative Medicine and Public Health, DOI: 10.3961/jpmph.16.066
Breastfeeding and ovarian cancer risk: a systematic review and meta-analysis of 40 epidemiological studies
This review of five cohort studies and 35 case-control studies including 17,139 women with ovarian cancer showed a 30% reduced risk of ovarian cancer when comparing the women who had breastfed with those who had never breastfed. When the participants were restricted to only parous women, there was a slightly attenuated but still significant risk reduction of ovarian cancer. Breastfeeding was inversely associated with the risk of ovarian cancer, especially long-term breastfeeding duration that demonstrated a stronger protective effect.
Li, DP, et al (2014). Breastfeeding and ovarian cancer risk: a systematic review and meta-analysis of 40 epidemiological studies, Asian Pacific Journal of Cancer Prevention, PMID: 24998548
Breastfeeding and ovarian cancer risk: a meta-analysis of epidemiologic studies
This review of five prospective and 30 case-control studies were included in this analysis found that the risk of epithelial ovarian cancer decreased by 8% for every five-month increase in the duration of breastfeeding. The risk reduction was similar for borderline and invasive EOC and was consistent within case-control and cohort studies. Additional research is warranted to focus on the association with cancer grade and histologic subtypes of EOC.
Luan, NN, et al (2013). Breastfeeding and ovarian cancer risk: a meta-analysis of epidemiologic studies, The American Journal of Clinical Nutrition, DOI: 10.3945/ajcn.113.062794
Breastfeeding and risk of epithelial ovarian cancer
In this Australian population-based case-control study of epithelial ovarian cancer between 2001 and 2005 (1,092 cases and 1,288 controls) completing a reproductive/lifestyle questionnaire, researchers found a strong inverse association between total duration of breastfeeding (all episodes combined) and ovarian cancer occurrence that appeared to be independent of parity. However, individual episodes of lactation beyond 12 months conferred no appreciable additional benefit. The relation with breastfeeding appeared to vary by histological subtype such that we saw no association between duration of breastfeeding and borderline serous cancers or mucinous cancers, but inverse associations for the other subtypes, although these were not always statistically significant.
Jordan S, Siskind V, Green AC et al (2009) Breastfeeding and risk of epithelial ovarian cancer. Cancer Causes Control.