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Experts know that endometriosis affects fertility—but the mechanisms aren’t quite clear. Is there a relationship between endometriosis and egg quality? Let’s explore.

Endometriosis and infertility

Endometriosis is a condition in which the tissue that lines the uterus—the endometrium—grows on other organs inside a woman’s body, like the ovaries or the Fallopian tubes. These tissues grow, breakdown, and bleed just like the endometrium inside the uterus, except because they’re outside, this cycle can cause irritation or inflammation in surrounding organs or even produce scar tissue, known as “adhesions,” that can cause organs to attach to each other.

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We know that an estimated 40% of unexplained infertility is due to endometriosis. The obvious explanation is that the endometriosis growth or scar tissue adhesions can damage the ovaries or Fallopian tubes, block the movement of eggs through the Fallopian tubes, or prevent sperm from entering. But in fact, it may be little more complicated—there may be a deeper connection between endometriosis and egg quality.

Correlation between endometriosis and egg quality?

Studies (1, 2) demonstrate that women with endometriosis have fairly high pregnancy rates when they undergo IVF with donor eggs from another woman without endometriosis. However, when women without endometriosis do IVF using donor eggs from women with endometriosis, success rates are “significantly reduced.”

One study demonstrated that embryos created from the eggs of women with endometriosis during IVF had lower rates of fertilization and development than embryos from women without endometriosis. Additionally, studies have demonstrated that women with endometriosis experience a higher rate of early pregnancy loss than other women. We know that miscarriage is often the result of poor egg quality (eggs that are genetically abnormal).

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These studies lead experts to consider that it’s not merely physical obstacles that are causing fertility difficulties—there may also be a connection between endometriosis and egg quality.

The potential relationship between endometriosis and egg quality

There are several theories surrounding the relationship between endometriosis—and the symptoms of endometriosis—and egg quality.

An inflammatory environment for eggs

One potential mechanism for the connection between endometriosis and egg quality reduction is that endometriosis may create an inflammatory environment in the reproductive system. Some studies indicate that endometriosis is associated with higher levels of certain inflammatory substances, such as macrophages (a type of white blood cell that helps your body eliminate cellular debris and foreign organisms) and cytokines (molecules that can promote inflammation as part of your body’s immune response).

Some experts believe that the presence of these inflammatory substances in the reproductive system can be toxic to the eggs, affecting their quality. To quote one report, the fact that women with endometriosis have higher levels of these inflammatory substances and lower pregnancy rates seems to suggest that “endometriosis-related toxic exposure may result in embryos that are defective… This may explain both the low implantation rate and the high incidence of early spontaneous abortion [miscarriage].” The “defective embryos” the researchers refer to here are the result of abnormal eggs.

Endometriomas (AKA “chocolate cysts”)

Endometriomas are cysts that form in or on the ovary in women with endometriosis. They’re called “chocolate cysts” because they’re filled with a dark brown combination of menstrual debris, fragments of endometrial tissue, thickened blood, and more. The presence of endometriomas is associated with increased risk of early pregnancy loss and lower embryo quality; they may be one explanation for the connection between endometriosis and egg quality.

The ovaries produce the reproductive hormones progesterone and estrogen, which are important to the maturation of an egg. Some experts believe that hormone imbalances in the ovary, such as may be caused by endometriomas, can affect egg development and egg quality. In addition to potentially being the cause of the connection between endometriosis and egg quality reduction, endometriomas affect egg count; women with endometriomas typically have fewer eggs in the surrounding ovarian tissue.

Reduced blood flow

Another potential source for the endometriosis and egg quality correlation goes back to the scar tissue present in the reproductive system of a woman with endometriosis. That scar tissue can compromise blood flow to or within the ovaries, meaning the ovaries are getting less oxygen than they would otherwise. The lower oxygen levels may result in eggs that don’t mature properly, and are therefore not able to fertilize, implant, or develop in a healthy way.

Endometriosis and egg freezing

The relationship between endometriosis and egg count—as well as the potential connection between endometriosis and egg quality—are both excellent reasons for women with endometriosis to consider egg freezing.

Because endometriosis, as explained by endometriosis expert and OB/GYN Dr. Iris Orbuch, “decreases a woman’s ovarian reserve [and] decreases fertility by either an anatomical distortion or via inflammation,” women with endometriosis who aren’t yet ready to get pregnant are great candidates for egg freezing. “I always encourage my patients to consider egg freezing long before they are ready to consider child bearing,” Dr. Orbuch explains.

Learn more about egg freezing, endometriosis, and egg quality by contacting our team.