The quality of a woman’s eggs is particularly affected in ovaries with larger cysts — or endometriomas, sometimes called “chocolate cysts” — that are greater than 3 cm (1.2 inches) in diameter.
Despite surgical removal of ovarian cysts, a decline persists in the ovaries’ capacity to provide eggs, the study also suggests.
The study, “Oocyte quality in women with infertility associated endometriosis,” was published in the journal Gynecological Endocrinology.
However, the mechanisms of endometriosis-related infertility are not well-understood.
It is thought that infertility may be caused by a number of problems linked to the disease, including anatomical distortions in the pelvis, the formation of endometrial lesions on ovaries, hormonal changes, or altered egg (oocyte) quality.
But knowledge of egg quality in women with endometriosis has been limited. Oocytes ready for fertilization — at a later stage of development — are difficult to obtain for research. In addition, non-invasive markers of quality based on observing alterations in the structure, or morphology, of oocytes may not be reliable.
Recognizing this problem, a team of researchers sought to assess the quality of oocytes in women with infertility associated with endometriosis.
The study was conducted by scientists at the Medical Institute of the RUDN University and the Nova Clinic, a center for reproduction and genetics, in Russia, between 2018 and 2019. It included infertile women, ages 24 to 40, who underwent in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) procedures.
Participants were divided into three groups. Group 1 involved 50 patients with recurrent endometriomas, the ovarian cysts related to endometriosis. The second set of patients, group 2, included 50 women who had undergone surgical removal of endometriomas. The control group, or group 3, included 30 patients without endometriosis, but who had tubal factor infertility. Tubal factor infertility, which accounts for 25-30% of all infertility, is caused by obstructions in the fallopian tubes that connect the ovaries to the uterus. The condition prevents the sperm and egg from meeting.
Oocyte quality was determined across all IVF/ICSI cycles using several measures. The researchers assessed the number of antral follicles — ovarian follicles with the potential to release an oocyte — which were counted by ultrasound. They also noted the number of oocytes collected from each woman. The investigators also evaluated the main morphological characteristics of the oocytes, including their shape, uniformity of their cytoplasm (a solution that fills most of the cell), and the presence of an intact first polar body. The polar body is a small cytoplasm “body” that is driven out of the oocyte to enclose the excess DNA formed during oocyte maturation and sperm fertilization.
The results showed that both groups of women with endometriosis-associated infertility — groups 1 and 2 — had fewer antral follicles, indicating a lesser ability by the ovaries to produce oocytes, known as ovarian reserve, in comparison with the control group. In line with this observation, fewer oocytes were recovered from the ovaries of the endometriosis patients.
Ovaries with endometriomas were particularly weak at producing oocytes, especially when these cysts were larger than 3 cm in diameter. This occurred in four patients in group 1 and one patient in group 2.
Morphological analysis further revealed that endometriosis patients produced more immature oocytes — ones at early stages of development called metaphase I, MI, or germinal vesicle stage, GV. These women also produced less high-quality oocytes, meaning those in metaphase II, or MII, which are ready for fertilization. This indicated a decline in the quality of the oocytes.
Again, such deterioration was observed from ovaries containing larger endometriomas of more than 3 cm in diameter.
Individual analyses demonstrated that every fourth oocyte extracted from an ovary containing an endometrial cyst had structural changes and various signs of degenerative changes.
Importantly, it was more difficult to induce the maturation of oocytes in vitro (in petri dishes in a lab) to a fertilization-ready stage when they were collected from endometriosis patients.
“The results of this study allow to conclude that endometriomas negatively affect quality of oocyte and ovarian reserve, whereas endometriomas after cystectomy [surgical removal of cysts], has a deleterious and sustained effect on ovarian reserve,” the researchers said.
Despite these findings, the scientists said more research is needed to determine how the alterations seen in the eggs’ morphology affect egg quality. Additional study is needed for researchers to clarify whether these changes cause a loss of quality in the eggs, or affect their ability to produce successful pregnancies.