London: Researchers have found that endometriosis -- a chronic condition affecting around 10 per cent of women -- may be the reason behind their difficulty in getting pregnant.

Endometriosis -- chronic abdominal pain, irregular periods, and lowered fertility -- is strongly associated with infertility and up to 50 per cent of women who require infertility treatment have it, the study said.

In order to become pregnant, a woman must produce a mature egg, which then is released to be fertilised.

However, the study found that eggs in women who have endometriosis are affected by a very hostile uterine environment that lowers fertility.

In women with endometriosis, ability of the egg to mature gets blocked as it suffers serious damage by exposure to follicular fluid and the egg quality gets severely compromised, the researchers explained.

"The study found that fluid from the follicles of patients with endometriosis was found to block egg maturation by generating free-radical chemicals called Reactive Oxygen Species (ROS) in the egg, which damage their DNA. This damage caused the egg not to mature, and hence it could not be fertilised," added Simon Lane, doctoral student at the University of Southampton. 

More research is now needed to investigate whether such damage caused by endometriosis is treatable or preventable, Lane said.

According to researchers, the effects of endometriosis on eggs could be prevented by antioxidants, as they can decrease ROS levels and help eggs to mature. 

The paper was published in the journal Scientific Reports.