Pain and infertility are two main symptoms of endometriosis. It is estimated that women who suffer from endometriosis are 30-50% more likely to be infertile.

The mechanisms of endometriosis-associated infertility are still unknown. It may be caused by the formation of endometrial lesions on ovaries, anatomical distortions in the pelvis, hormonal imbalance or the inferior quality of the eggs.

Researchers assessed the quality of oocytes (eggs) in women with infertility associated with endometriosis and found that the number and quality of eggs they produce are negatively affected by ovarian cysts, thus also affecting the outcomes of assisted reproduction.

The quality of a woman’s eggs is particularly affected when a large ovarian cyst (endometrioma) sometimes called chocolate cyst has a diameter larger than 3 cm.

Surgical removal of ovarian cysts does not restore the ovaries’ capacity to produce eggs, the study suggests. “Endometriomas negatively affect the quality of oocyte and ovarian reserve, whereas endometriomas after cystectomy, have a deleterious and sustained effect on ovarian reserve” according to the researchers.

Infertile reproductive-aged women, between 29 and 40 years who underwent IVF and ICSI procedures participated in the study, conducted between 2018 and 2019 by scientists at the Medical Institute of the RUDN University and Nova Clinic, a center for reproduction and genetics, in Russia.

The women were divided into three groups. Group 1 included 50 patients with recurrent endometriomas, the ovarian cysts related to endometriosis. Group 2 included 50 women who had undergone surgical removal of endometriomas. Group 3, the control group included 30 patients without endometriosis, but who had tubal factor infertility.

Oocyte quality was determined across all IVF / ICSI cycles. The researchers assessed the number of antral follicles (ovarian follicles with the potential to release an oocyte) which were counted by ultrasound. They counted the number of oocytes collected from each woman and evaluated the main morphological characteristics of the oocytes.

The results showed that both groups of women with endometriosis-associated infertility had fewer antral follicles, indicating a lesser ability by the ovaries to produce oocytes, in comparison with the control group. Fewer oocytes were recovered from the ovaries of endometriosis patients.

The morphological analysis further revealed that endometriosis patients produced more immature oocytes -ones at early stages of development called metaphase I or germinal vesicle stage. These women also produced less high-quality oocytes, those in metaphase II, which are ready for fertilization. This indicated a decline in the quality of the oocytes. Such deterioration was observed from ovaries containing larger endometriomas of more than 3 cm in diameter.

Individual analyses demonstrated that 25% of the oocytes extracted from an ovary containing an endometrial cyst had structural changes and various signs of degenerative changes.

At the same time, it was more difficult to induce the maturation of oocytes in the lab to a stage they are ready for fertilization when they were collected from endometriosis patients.

The study, “Oocyte quality in women with infertility associated endometriosis” was published in the journal Gynecological Endocrinology.