Breastfeeding linked to lower risk of endometriosis

The longer a woman breastfeeds, the less likely she will have problems with endometriosis, according to a study which followed thousands of women for more than 20 years.  Endometriosis is a chronic, painful gynecologic disorder in which the tissue that forms the lining of the uterus grows outside of the uterine cavity. Around 10 percent of women in the United States have this condition.  As a result, women with endometriosis suffer from chronic pelvic pain, painful periods, and pain during intercourse.

Study details

This study, led by the Brigham and Women’s Hospital in Boston, Massachusetts, and published in the British Medical Journal, used data from the Nurses’ Health Study II which began in 1989.  Researchers studied participants who had had at least one pregnancy during the time of the study – women who had been diagnosed with endometriosis or cancer before the 1989, were removed from the study which left 72,394 women to analyze.  This included 3,296 women diagnosed with endometriosis which was confirmed by laparoscopy, a procedure used to examine adnominal organs.  

Each participant answered detailed questionnaires to determine how long each breast-fed, who exclusively breast-fed (without introducing formula or solid food), and how much time elapsed before a woman’s menstrual cycle resumed.

Results from the study

Results from the study showed that for every 3 additional months of breastfeeding per pregnancy, there was an 8 percent reduced risk of endometriosis.  For women who exclusively breastfed, the reduced risk of endometriosis rose to 14 percent.

Also found was that women who had breastfed for a total of 36 months or more during their reproductive lifetime, had a 40 percent reduced risk for endometriosis compared with women who had never breastfed.  Even if the woman had exclusively breastfed for only 18 months over her reproductive lifetime, her risk for developing endometriosis was lowered by 30 percent.

Why does breastfeeding appear to lower risk of endometriosis?

What the study definitively showed was the association between the longer a woman breastfeeds, the lower her chance of being diagnosed with endometriosis.  So the longer a woman breastfeeds, this appears to be a modifiable behavior in reducing the risk of endometriosis among women after having a baby. 

The logical explanation for this finding would be due to the absence of periods after pregnancy since the menstrual cycle is delayed when breastfeeding.  This would explain some of the reason for the finding but other factors are likely at play too.  One factor is that breastfeeding results in different hormonal changes involving the hormones of oxytocin, estrogen, and gonadotropin-releasing hormone.  There is evidence that these hormones may play a role in endometriosis development.

Researchers however, cautioned that this study does not prove that breastfeeding prevents endometriosis but that it appears to prevent the severe pain caused by the condition which makes it less likely for a woman to be diagnosed with it.

Even if that is the case, then it would still make sense to advise and encourage any woman of child-bearing age who has endometriosis, to strongly consider breastfeeding her baby to help possibly prevent the pain of endometriosis and to also provide the best nourishment and health benefits breastfeeding has to offer for her growing infant.