Endometriosis cells can be found on reproductive organs like the ovaries and fallopian tubes, which can cause scarring and adhesions which ‘stick’ some of the pelvic organs together. This can stop them from working in the same way as someone who doesn’t have endometriosis. Endometriosis in the ovaries (endometriomas) might also affect the quality of the eggs that they produce, making them less likely to successfully develop into a baby after fertilisation.

Diagram of the female pelvic area showing that adhesions can pull organs out of position
Adhesions are bands of scar tissue that can attach organs to each other and can pull organs out of position

Endometriosis can also cause chronic inflammation inside the body. Inflammation is a normal bodily reaction to things that might harm it, such as injury or infection. Because endometriosis cells grow in places that they shouldn’t, the area becomes inflamed, releasing pain signals, hormones and antibodies to try to fight back. It’s possible that this long-term inflammation and the stress it puts on the body can create a less healthy environment for an egg to be fertilised, and for a baby to grow.

Many people with endometriosis delay starting a family until their endometriosis is resolved. Given how long it can sometimes take to get diagnosed and treated for endometriosis people often start trying to conceive later than the national average of 30 years. Unfortunately, fertility declines with age, especially after the age of 34. Endometriosis may therefore affect fertility because it causes people to start trying when their fertility has already begun to decline.