What is endometriosis?

Bottom lineEndometriosis is a condition affecting about 1 in 10 women where tissue similar to the uterine lining grows outside the uterus, thickening and bleeding with the cycle and causing inflammation, scar tissue, and adhesions; main symptoms include severe period pain, chronic pelvic pain, pain during sex or with bowel or bladder movements, heavy bleeding, fatigue, and difficulty conceiving. It's often missed for years because symptoms vary and severe period pain gets normalized, but it's manageable with the right care.

Endometriosis is a condition where tissue similar to the lining of the uterus grows outside it - on the ovaries, fallopian tubes, and other pelvic organs. It affects roughly 1 in 10 women of reproductive age.

What happens

This tissue behaves like the uterine lining: it thickens and bleeds with your cycle. But because it's outside the uterus, the blood has nowhere to go, causing inflammation, pain, scar tissue, and adhesions that can stick organs together.

Main symptoms

• Severe period pain that doesn't ease with usual painkillers
• Chronic pelvic pain, sometimes beyond your period
• Pain during or after sex
• Pain with bowel movements or urination, especially during periods
• Heavy or irregular bleeding
• Fatigue
• Difficulty conceiving (endometriosis is a common factor in infertility)

Why it's often missed

Symptoms vary, overlap with other conditions, and severe period pain gets normalized - so diagnosis takes an average of several years. Pain severity doesn't always match how much endometriosis is present.

Why it matters

It's a chronic condition that can affect quality of life and fertility, but symptoms are manageable with the right care, and 2026 guidelines emphasize earlier, tailored treatment.

Read our endometriosis 2026 guidelines article and period pain vs endometriosis pain.

Femora helps you track pain and symptoms over months - the evidence that speeds an endometriosis diagnosis.