What’s the difference between period pain and endometriosis pain?

Menstruation, or a period, is the bleeding that occurs about monthly in healthy people born with a uterus, from puberty to menopause. This happens when the endometrium, the tissue that lines the inside of the uterus, is shed.

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Endometriosis is a condition that occurs when endometrium-like tissue is found outside the uterus, usually within the pelvic cavity. It is often considered a major cause of pelvic pain.

Pelvic pain significantly impacts quality of life. But how can you tell the difference between period pain and endometriosis?

Periods and period pain

Periods involve shedding the 4-6 millimetre-thick endometrial lining from the inside of the uterus.

As the lining detaches from the wall of the uterus, the blood vessels which previously supplied the lining bleed. The uterine muscles contract, expelling the blood and crumbled endometrium.

The crumbled endometrium and blood mostly pass through the cervix and vagina. But almost everyone back-bleeds via their fallopian tubes into their pelvic cavity. This is known as “retrograde menstruation”.

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The process of menstrual shedding is caused by inflammatory substances, which also cause nausea, vomiting, diarrhea, headaches, aches, pains, dizziness, feeling faint, as well as stimulating pain receptors.

These inflammatory substances are responsible for the pain and symptoms in the week before a period and the first few days.

For women with heavy periods, their worst days of pain are usually the heaviest days of their period, coinciding with more cramps to expel clots and more retrograde bleeding.

Many women also have pain when they are releasing an egg from their ovary at the time of ovulation. Ovulation or mid-cycle pain can be worse in those who bleed more, as those women are more likely to bleed into the ovulation follicle.

Around 80% of adolescents experience period pain that need time off from school and miss activities. These symptoms are too often normalised, without validation or acknowledgement.