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Sampson’s Theory of Retrograde Menstruation

What is Sampson's theory of retrograde menstruation?

Sampson's Theory of Retrograde Menstruation

There are many hypotheses examining the origins of endometriosis, but perhaps the oldest is Sampson’s theory of retrograde menstruation. This term is defined as the backward flow of menstrual blood. In short, Sampson’s theory proposes that the retrograde flow of menstrual blood is linked to the development of endometriosis.

How could retrograde menstruation cause endometriosis development?

Retrograde menstruation refers to a woman’s menstrual blood flowing back into her body during her period. Sampson’s theory proposes that when this occurs, the menstrual debris carries sloughed-off tissue from the endometrium, which is the lining of the uterus that sheds monthly. These endometrial cells will then be carried backward through the fallopian tubes and to the ovaries and surrounding pelvic cavity, where they can implant and cause the development of endometriosis.

How does this relate to normal ovulation?

Ovulation—the hatching of eggs from the ovaries—occurs in a woman’s body each month. Fourteen days later, if there is no pregnancy, she has her menstrual period, during which her body naturally sheds the endometrium. If the menstrual flow properly exits from her body, the flow carries the endometrium with it through the cervix, the opening of the uterus that connects to the vagina. The cervix is small, strong, and tight; it opens to allow menstrual blood out, but if a woman becomes pregnant, also keeps a baby in the uterus for nine months.

If the menstrual flow does not exit as it should, the menstrual blood may leak back into the body through the natural openings in the fallopian tubes. The debris can then implant in areas outside of the uterus in the pelvis and creates an abnormal growth of cells: endometriosis with inflammation. These lesions will then grow with further menstrual cycles and unlike the endometrium that naturally leaves the body, there is no way for the implants to exit the body. The inflammation and endometriosis grows and continues to spread. This is why endometriosis can be thought as menstrual periods that are literally stuck inside of a woman’s body.

Is retrograde menstruation normal?

While the thought of menstruation flowing backward may seem daunting, it is, in fact normal for most women to have some form backward flow. Because tissue and fluid can drain harmlessly through the body’s natural mechanisms, you may not even feel any symptoms of this.

What causes retrograde menstruation?

There is no known cause of retrograde menstruation, but it seems to be normal in most women. Nevertheless, uterine peristalsis has been proposed as having a connection to retrograde menstruation. This is the contraction of the muscle wall of non-pregnant females, which has been heavily studied in many fertility cases. Dysfunction of the normal contraction cycle of the uterus has been speculated to have a connection to endometriosis development and retrograde menstruation. More research must be conducted as many studies to date are directed at seeing what role uterine peristalsis plays in endometriosis development as opposed to specifically retrograde menstruation.


If one has retrograde menstruation, they will experience endometriosis.


Retrograde menstruation is actually common in most women. Its relationship with the exact cause of endometriosis is still unknown and requires further study and research.

Critiques against the theory of retrograde menstruation?

Like any theory, retrograde menstruation is highly debated amongst the medical community. Many doctors, while certainly supporting that retrograde menstruation does exist, question the role it plays in the development of endometriosis. These experts will often favor a more genetic-based theory or one that can support the fact that certain individuals are more predisposed to the disease at birth. Some will argue that if endometriosis was indeed caused by retrograde menstruation then lesions that are not implanted, such as some of those not on the peritoneum (lining of the abdomen), would be much easier to remove upon surgery. Instead of needing to be cut out through excision surgery, the endometriosis could simply be removed with a suitable suction tube.

Others argue that according to Sampson’s theory, the older one gets, the more retrograde menstruation should take place and thus more endometriosis should occur. However, upon pelvic mapping, in which surgeons identify the location and distribution with the pelvic cavity, many have found that this is not the case. These critics have found that there is no correlation with age and the severity and extent of the disease within the pelvic cavity, and thus Sampson’s theory must not be entirely accurate.

Retrograde menstruation as a cause versus a trigger

While medical debate brings on those on contrasting sides, there are also those who take a more middle ground approach. Some providers believe that although retrograde menstruation may not be the exact cause of endometriosis development, it certainly seems to play a role in the process. These theorists will often propose that retrograde menstruation serves more as a triggering factor for patients who are predisposed to develop endometriosis, either due to genetics or some other factor. Thus many see Sampson’s theory of retrograde menstruation as not a sole cause, but rather a piece to the puzzle of the complicated etiology of endometriosis.


  1. Harry Reich. “Endometriosis: Hormonal or Surgical? My Reality.” A powerpoint presentation was given at the Breast, Ovary, and Endometriosis medical conference. October 28th, 2017. https://www.endonews.com/efa-medical-conference-2017-endometriosis-hormonal-or-surgical-my-reality-presentation-by-dr.-harry-reich
  2. Leyendecker G. et al., “Uterine peristaltic activity and the development of endometriosis.” Annals of the New York Academy of Sciences. 2004.