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About 1 in 20 women who can't get pregnant have a condition called endometriosis.¹ This is a disease of the lining of the womb. The lining is called the endometrium.

In endometriosis, the cells that normally grow in the endometrium are growing in other places outside the womb. The cells might grow around the ovaries and fallopian tubes, or the bowel. The endometrial tissue outside the womb usually bleeds at the same time as the woman has her period. This is painful and can scar and damage these organs.

Doctors aren't sure why endometriosis lowers the chances of a woman getting pregnant. It may affect the quality of the egg, damage the sperm, cause scarring or make it more difficult for the sperm to fertilize the egg. Although endometriosis can be painful, it's often not diagnosed until a woman has difficulty becoming pregnant.

For more information, see our articles on Endometriosis.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.