Women with endometriosis are up to twice as likely to develop inflammatory bowel disease as those without this reproductive disorder, suggests a large study published online in Gut.
And the effect can last for up to 20 years after their diagnosis of endometriosisa condition in which cells from the womb lining implant in other areas of the body.
Endometriosis is relatively common, and thought to affect as many as one in 10 women during their child bearing years.
The researchers tracked the long term health of more than 37,000 Danish women who had been admitted to hospital with endometriosis between 1977 and 2007.
During a monitoring period, which lasted an average of 13 years, 320 of these women developed inflammatory bowel disease228 ulcerative colitis and 92 Crohn's disease. These figures equate to an increased risk of developing inflammatory bowel disease of 50% compared with women in the general population.
When the analysis was restricted to women whose endometriosis was verified surgically, the risk increased further to 80%, and the effect persisted for more than 20 years after the initial diagnosis.
The average time lag between a diagnosis of endometriosis and the development of inflammatory bowel disease was around 10 years.
Both inflammatory bowel disease and endometriosis are chronic inflammatory disorders, which typically begin in young adulthood, affect the bowel, and cause abdominal pain.
The authors conclude that the explanation for the link between the two disorders may lie in common causes or the effects of treatment for endometriosis.
Some research suggests that long term use of oral contraceptives, which are frequently used to treat endometriosis, may increase the risk of developing inflammatory bowel disease.