How Does Endometriosis Cause Infertility?
Reviewed by: HU Medical Review Board | Last reviewed: June 2018
Endometriosis is often associated with, or causes, infertility. It has been estimated that 20-50% of women with infertility are diagnosed with endometriosis, however, not every woman with endometriosis will be infertile.1,2 Infertility is the inability to become pregnant or carry a baby to term. It's important to note that endometriosis does not always cause complete infertility. In some cases, endometriosis may decrease a woman's chances of becoming pregnant, however, pregnancy is still possible (subfertility). In other cases, a woman's fertility may not be affected at all. For some women whose fertility is impacted by their endometriosis, the cause may be obvious, such as scarring that blocks the fallopian tubes or that has impacted the structure of key reproductive organs. In other cases though, the cause of infertility may not be obvious. Some common theories on how endometriosis might impact fertility are below.
Scarring and distortion of anatomy
Severe scar tissue, adhesions, or scarring of the key components of the reproductive system are some of the more obvious reasons for infertility. In some cases, scarring may impact the fallopian tubes and prevent an egg from traveling from the ovaries to the uterus for fertilization and growth. Additionally, scarring in other places of the female reproductive system, including the outside of the uterus or other surrounding structures, may hinder a fetus's overall ability to grow and develop.
Occasionally, ovarian cysts or scarring may prevent the ovaries from releasing an egg each month, or may reduce the probability of an egg being released. Additionally, surgery to remove cysts can reduce the ovarian reserve (a woman's stored eggs and the health of those eggs), further impacting fertility. All of a woman's unfertilized eggs are made while she is developing in her mother's womb. Unlike males who constantly produce new sperm cells, a woman is born with a supply of eggs that stay with her throughout her entire reproductive life.2-5
Issues with the immune system
Some theories as to why endometriosis may develop include the potential malfunctioning of the immune system. Endometriosis can co-occur with several autoimmune conditions, and it has been thought that the body's immune system does not recognize that endometrial tissue is growing in the wrong places, and allows it to continue to grow and shed in areas where it shouldn't. This same idea may apply to a developing embryo. It may be possible that the body's immune system mistakenly thinks that the embryo is a foreign invader or other potentially dangerous cell type. This may lead the body to destroy the embryo, preventing it from growing within the uterus. Overall, in this hypothesis, the body recognizes "good" cells as bad, and "bad" cells as good, allowing endometriosis to develop, while preventing the growth of a fetus. This idea may also be the case for incoming sperm cells. The body may mistakenly attack these cells and prevent them from fertilizing an egg.2-5
A common risk factor for endometriosis include müllerian anomalies or developmental irregularities within the reproductive system. In an embryo, the müllerian ducts develop into the majority of the female reproductive system. If this development is disrupted somehow, many different reproductive irregularities may occur. Some of these include the malformation of the endometrium tissue, developing an abnormally shaped uterus, or other malformations of the uterus, vagina, or cervix. Many of these abnormalities not only increase an individual's risk of developing endometriosis, but also can greatly impact fertility.1,3,6
Can I still get pregnant?
Many women with endometriosis still can, and do, get pregnant. The impact on fertility as a result of endometriosis can vary significantly from person to person. A good way to determine the impact on your fertility is to talk with your doctor or healthcare team. Your doctor may be able to assess any scarring you may have, as well as talk about any personal risk factors you may possess that could lead to infertility or decreased fertility. Many women with endometriosis utilize fertilization-enhancing treatment options. Some of these include, but are not limited to: