Endometriosis and Fertility

Endometriosis and Fertility

What is Endometriosis??

Endometriosis is a benign, inflammatory, chronic and incurable disease that affects the health and fertility of nearly 180 million women worldwide. To get a global idea, it affects 1 in 10 women of reproductive age. Although it is an increasingly known disease  in our society, there is still a large part of the population that is unaware of its existence and its effects.

The term endometriosis refers to the presence of endometrial tissue, that is, the tissue that covers the uterus on the inside that flakes or bleeds each time you have menstruation, outside the endometrial cavity.

Where can you find endometriosis?

The most common appearance is in the form of a cyst in the ovaries, but also in the thickness of the muscular wall of the uterus, called adenomyosis, or by the peritoneal cavity, between the intestinal loops or in the bladder, in the form of endometriotic implants. Although very rare, endometriosis has also been found in the lungs, nose, or even the brain.

Origin of endometriosis

Despite the advances and the investigations carried out to know the origin and development of the disease, it is still a field that is not fully understood. It is known that both genetics and external factors can influence, since it is more frequent to appear among relatives who suffer from it. It has also been linked to certain lifestyle habits, such as the intake of trans fats, a high level of stress, or exposure to certain environmental toxins.

On the other hand, its relationship with an altered immune system, as well as with certain autoimmune diseases such as psoriasis or autoimmune thyroiditis, makes us think of this factor as a possible determining agent together with other circumstances.

Endometriosis diagnosis

Its diagnosis is a challenge for professionals who are dedicated to it: that is the reason why many patients with endometriosis are not diagnosed.

Although, it is true that, thanks to a recent laxity in the way of diagnosing the disease provided by both national and international guidelines, this is changing.

Currently, the diagnosis could be made only with the symptoms and the presence of certain related factors. However, previously it was only possible by surgery, which made diagnosis very difficult.

The most frequent way of detecting the presence of the disease is due to the appearance on ultrasound of what is called a “chocolate cyst”, which is a cyst that appears on the ovaries, however, it is increasingly common to be able to visualize endometriosics implants in the hands of an expert professional and with a high resolution ultrasound scanner.

Symptoms of endometriosis

Painful periods, also called dysmenorrhea, are the most common symptom of endometriosis, although it is also closely related to chronic pelvic pain or painful sexual intercourse (dyspareunia).

Depending on the location of the implants, it has also been associated with gastrointestinal symptoms (diarrhoea/constipation) or with blood in the urine during menstruation. In fact, many patients presenting these symptoms have previously consulted a physician specializing in the digestive system.

The impact of endometriosis on fertility

Amongst all known symptoms, sterility is the one that causes more concern. According to statistics, 30% to 50% of patients with endometriosis are likely to face hardship when trying to get pregnant. This percentage might be lower, since, as pointed out, many patients have not been diagnosticated with the disease; still, it would be a significant share.

Nevertheless, it is not yet known why or how it affects fertility. The fact that there are different types of endometriosis (superficial endometriosis, ovarian endometriosis, deep endometriosis, adenomyosis and preitoneal endometriosis) and different stages, makes it very difficult to know which women are likely to suffer from infertility. And though it may seem that an increased severity would worsen the symptons and would increase the chances of infertility, not all studies are conclusive in this regard.

Depending on each patient, fertility may be affected by different causes; the most accepted theories are as follows:


ovarian endometriosis decreases the amount of healthy ovarian tissue, and chronic inflammation produces fibrosis on that area; both of them are considered the cause for which patients with endometriosis are more likely to have a diminished ovarian reserve. There are two tests that may help understand the status of the ovarian reserve: an ultrasound scan to determine the number of antral follicles and a blood test to measure the anti-Müllerian hormone.


it has been shown that ovarian endometriosis boosts certain factors that are toxic to normal oocyte development, as well as the presence of pro-inflammatory cells. There is no way of knowing the status of egg quality, it can only be suspected after undergoing an in vitro fertilization


endometriosis causes inflammation and fibrosis, in other words, scar tissue, which makes structures adhere and distort. This may cause a completely distorted uterus with abnormal contractions, which is related to an abnormal sperm transport towards the Fallopian tubes. A uterine contractions study during the implantation window may help understand the status of uterine contractility.


adhesions and fibrosis caused by an inflammation status may affect both the functionality of the tubal structure and its anatomy, with the presence of hydrosalpinx or hematosalpinx. We can check tubes permeability through a hysterosalpingography with contrast dye (HyCoSy).


this brings us back to the theory that inflammation mediators cause the immune system to provoke a pathological environment, thus the uterus is not able to develop a receptive endometrium on the implantation window. In addition, the relation of endometriosis to progesterone resistance is well known. This could be partly clarified by measuring progesterone levels during the implantation window.


there is evidence that patients with endometriosis are more likely to have an abnormal microbiome. Whether this is a cause or a simple coincidence remains unknown; however, this could be another factor of patient’s fertility problems. Nowadays it is possible to know and restore the vaginal microbiome status.

Female fertility may be diminished by all these causes, together or separately. That is the reason why all patients suffering from endometriosis have to be informed about the relationship between this illness and sterility, as well as the possibility of egg freezing.



  • Adenomyosis and recurrent implantation failure
  • Endometritis: What is it? How can it be detected? How can it be cured?
  • A specially adapted diet for endometriosis

Dr. Belén Moliner, gynaecologist at Instituto Bernabeu

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