Science You Can Use: Breastfeeding may reduce ovarian cancer risk by up to 91%, finds new study.

One in 72 American women will be diagnosed with ovarian cancer sometime during their lives.

It’s a hard disease to detect, and is the most deadly of all gynecological cancers.  So prevention of ovarian cancer is especially important.

Past research has shown an association between breastfeeding and lowered risk of ovarian cancer, pointing to an estimated 27% increase in risk attributed to not breastfeeding.

But a new study has produced some even more dramatic numbers to illustrate this connection.

The study, carried out by Australian researchers in China, compared the breastfeeding history of about 500 women with ovarian cancer to a similar group of who did not have ovarian cancer.

What they found was a highly significant inverse relationship between breastfeeding and ovarian cancer, and a “dose response” effect – meaning that more breastfeeding and more births yielded more protection.

Specifically, they found:

Women who breastfed for more than 13 months were 63 percent less likely to develop an ovarian tumor than women who breastfed for less than seven months. The benefits jumped the longer that women breastfed. The researchers found that mothers who had three children and who breastfed for over 31 months were up to 91 percent less likely to suffer from ovarian cancer than women who breastfed for under 10 months.

Note that the comparisons here were between mothers who breastfed for different durations, not between women who did and did not breastfeed.  This is also impressive because the median age for diagnosis of ovarian cancer in the U.S. is 63 – many years after the childbearing period in women’s lives.  The average age of participants in this study was 59.

Why would this be?  One theory about the development of ovarian cancer is that the more ovulations a woman has, the higher the risk of cancer.  Of course, pregnancy and breastfeeding suppress ovulation (not necessarily for the full duration of breastfeeding).

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