Breastfeeding and the Risk of Ovarian Cancer: A Meta-Analysis

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The aim of this meta-analysis was to assess the association between breastfeeding and risk of ovarian cancer.


Relevant observational studies were identified by a search of the MEDLINE and EMBASE databases through December 2012. Summary odds ratios (ORs) for ovarian cancer, comparing women who had breastfed with women who had not, were calculated using a random-effects model. A dose–response meta-analysis assessed the risk of ovarian cancer by breastfeeding duration.


A total of 19 studies were included in the meta-analysis. Compared with women who had not breastfed, women who had breastfed had a significantly decreased risk of ovarian cancer, with an OR of 0.66 (95% CI, 0.57-0.76; P < .001). We observed an inverse linear relationship with breastfeeding duration: for every one-month increase in breastfeeding, the OR was 0.98 (95% CI, 0.97-0.99; P < .001). A nonlinear association was also apparent, with a sharp decrease in the OR when breastfeeding duration was 8 to 10 months. There was evidence of heterogeneity (I2 = 83.9%). No publication bias was found (Begg test, P = 0.89; Egger test, P = 0.89).


Breastfeeding reduces the risk of ovarian cancer proportional to duration. Breastfeeding for 8 to 10 months may be most effective for reducing the risk of ovarian cancer.

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