Endometriosis and infertility are associated. The real question is: Does always endometriosis causes infertility? How endometriosis might cause infertility? These two questions are the key t understand if endometriosis should worry to everybody or just in some specific situations (in this article, I will analyze the endometriosis from the infertility point of view only and, therefore, I will omit comments related with pain and other type of symptoms).

What is endometriosis?

Endometriosis is a hormone-dependent trait (which means that it grows with hormones) and impacts in women’s health. Obviously, it appears in reproductive age (as hormones are higher) and impacts on physical, psychological and social spheres. In easy words, endometriosis means that endometrial cells (those cells that are usually in the inner layer of the uterus) are implanted in another site, generating inflammation, among other consequences. The most common site for endometriosis is the pelvis although it could be found in other anatomical regions. About one every 8-10 women has endometriosis and it is present in one every three women with infertility.

Do all women with infertility have to be evaluated for endometriosis?

Laparoscopy is the classic method to diagnose endometriosis. Currently there are some other non-invasive methods with more or less accuracy. However, the decision of performing a routine laparoscopy (or other test) to diagnose endometriosis should be based on the intervention  that will be applied when with result of the diagnostic method. In other words, laparoscopy (or other test) should be prescribed if the intervention is able to modify the infertility prognosis. Otherwise, if there is no effective intervention, the diagnostic test should have no place

When may endometriosis cause infertility?

There is high quality evidence showing that endometriosis is associated with pelvic adhesions which could lead to a tubal disease, in some cases. Besides, the endometriomas (cysts of endometriosis in the ovaries) might reduce the ovarian reserve. However, the available evidence is not clear whether the endometriosis impacts on egg quality or endometrial receptiveness. Recently, the peer-reviewed journal Fertility and Sterility published a couple of papers about this. One of them authored by Dr Miravet-Valenciano showed that endometrial molecules associated with embryo implantation don’t vary the grade of expression in women with endometriosis, regardless the endometrial stage. In the same volume of that journal, Bruce A. Lessey wrote an article  showing that, on the other hand, inflammatory factors are more prevalent in the endometrium of women with endometriosis, which could impact in the reproductive prognosis. The quality of the published evidence is low and, therefore, the explantations that support both points of view are only based on physiological issues and not on good quality scientific studies.

So, should I be evaluated for endometriosis?

Endometriosis could be found in some of the typical screening tests done to a couple with infertility. For example, hysterosalpingography can show tubal obstructions and ultrasound can find endometriomas. Both findings are importante as the change the approach of the reproductive treatment. However, is it necessary to know about the presence of endometriosis not found in those two mentioned tests? The answer should be based on the interventions that we can do to improve the prognosis and not just in performing the diagnosis of this. Therefore, even when endometriosis could impact in the reproductive outcome, I would ask: does any intervention on the endometriosis improve the reproductive outcome in a woman with this disease?

The answer is not simple and, unfortunately, I am not able to respond that question here. In a systematic review published some few years ago, the authors showed that patients that underwent IVF and had had a surgery for endometriosis, also had lower pregnancy rates. However, the live birth rate remained the same. Therefore, the question is still unsolved: making a diagnosis of endometriosis and then treating it, will improve the reproductive outcomes? We don’t know yet. And that is why the laparoscopy, which was a routine more than a decade ago, is only done when there is a suspicion of endometriosis in which case the intervention could improve the prognosis of that patient.