What Is Retrograde Menstruation and Is It Dangerous?

During the normal menstruation process, menstrual fluid, consisting of the lining of the uterus and blood, flows downward through the cervix and exits the vagina. Sometimes, the direction of the period is the opposite menstrual blood flows upward through the fallopian tubes into the abdominal cavity. It is called retrograde menstruation. This might cause some pelvic pain and lighter-flow bleeding through the vagina. Is it dangerous? Why does it happen?

Key takeaways:

What is retrograde menstruation?


Retrograde menstruation is a process when the period of blood moves backward through the fallopian tubes into the area in the abdomen, called the peritoneal cavity, instead of flowing downwards and exiting through the vagina. Although this process sounds odd, it is quite usual to have retrograde periods and typically it is not dangerous.

Causes of retrograde menstruation

During the usual menses, menstrual fluid, consisting of endometrial tissue and blood, exits the body through the cervix and vagina. It happens because of synchronized uterine contractions, called uterine peristalsis. Retrograde menstruation often occurs when the contractions of the uterus are asynchronous, causing the menstrual fluid to flow backward through the fallopian tubes into the abdominal cavity.

Other conditions that may cause retrograde menstruation are ones that disrupt the natural flow of the period fluid, including uterine growths (polyps, fibroids), structural abnormalities or obstructions of the vagina or the cervix (narrow opening), and those that cause heavy menstrual flow.

However, it should be noted that retrograde menstruation is a normal process that occurs in nearly all menstruating women (up to 90%); therefore it is regarded as a natural occurrence that rarely causes problems.

Symptoms of retrograde menstruation

Usually, retrograde menstruation doesn’t induce any symptoms and can be unnoticed throughout life because it is a natural part of the menstrual cycle. The most popular symptom of retrograde menstruation is painful periods. The blood enters the peritoneal cavity, covers the pelvic organs, irritates the tissue, and causes inflammation and pain. Additionally, due to the backward flow of the period, less blood escapes the vagina, so some women observe lighter periods.

Risks of retrograde menstruation

It is believed that women with retrograde menstruation are more likely to develop endometriosis. Endometriosis is a condition when the tissue of the lining of the uterus grows outside the uterus. It can cause severe dysmenorrhea (painful periods), spotting, and cycle irregularities.


This theory was brought up by Doctor John A. Sampson, who studied the retrograde menstruation process and endometriosis in the 20th century. According to his theory, during retrograde menstruation, the menstrual flow, consisting of endometrial cells and blood, is carried through the fallopian tubes to the peritoneal cavity. The endometrial cells can cover the pelvic organs and pelvic walls. During each menstrual cycle, the endometrial tissue is stimulated to grow and thicken, causing inflammation, pain, and lesions. This may result in the development of endometriosis.

On the other hand, this theory is not entirely correct. If the theory was completely true, the rates of endometriosis would be almost as high as the rate of retrograde menstruation. As mentioned before, up to 90% of women experience retrograde menstruation, while the endometriosis rate is around 10%, according to the World Health Organization. Moreover, Sampson’s theory would mean that endometriosis occurs more often with age, which is not true.

Therefore, scientists believe that retrograde menstruation can be a risk factor for developing endometriosis, but not the root cause. Certainly, more research is vital to study the link between retrograde menstruation and endometriosis.

Diagnosis and treatment of retrograde menstruation

Typically, retrograde menstruation is not diagnosed as a condition. It can be diagnosed as a symptom of endometriosis.

Retrograde menstruation is a normal process and does not need any treatment. However, doctors may choose a treatment plan if it causes severe abdominal pain or other conditions, such as endometriosis.

To reduce dysmenorrhea, it is recommended to use non-steroidal anti-inflammatory drugs (NSAIDs).

In the case of endometriosis, doctors may prescribe hormonal drugs or suggest using other contraceptive methods to stop the menstrual cycle. Another option is surgical removal of the endometriotic lesions.

When to see a doctor

Although retrograde menstruation is common and may not induce any symptoms, it is recommended to consult your healthcare provider if you notice intense changes in your period flow, severe pelvic pain, nausea, or dizziness.


Retrograde menstruation is a natural process that many women experience. Although more research is needed, it is linked with a higher chance of developing endometriosis. If you notice any changes in the regularity, the flow of the period, or severe pain, consult with your healthcare provider for further examination.



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