Endometriosis is a condition that can cause pain and infertility.  Given its complexity, we sometimes oversimplify some facts.  Before we dive in, let's focus on the female reproductive anatomy, which can be divided into 3 key organs:
 

  • Ovaries: here  It is where the eggs grow and are released during ovulation.

  • Fallopian tubes: one  Once the egg is released from the ovary, it travels down the fallopian tubes where it can come into contact with sperm to become a fertilized embryo.

  • Uterus: Once the embryo has traveled through the fallopian tube, it is released into the uterus.  Specifically, this is where the embryo implants itself into the inner lining of the uterus, which provides nourishment for the embryo to develop into a healthy fetus.

Endometrial Cells

To understand endometriosis, it helps to understand the lining of the uterine walls, the endometrium, and the cells (known as "endometrial cells") that it is made of.  Endometrial cells are special: they grow abnormally fast in the presence of estrogens.  When they grow, they create a thick inner endometrial lining of the uterus and this helps ensure that an embryo can implant itself into the wall of the uterus.  An embryo needs a good implantation to ensure that it receives nourishment and can develop into a fetus.

 

When endometrial cells escape, that's endometriosis

Endometrial cells are useful when they are contained in the uterus, but when they escape from the uterus they wreak havoc.  When these cells land and establish themselves in other organs, they cause inflammation and regional damage.  In effect, this is endometriosis.

 

How Endometriosis Impacts Fertility

The presence of endometriosis can make it difficult for a woman to conceive.  Specifically, endometriosis can interfere with the following reproductive components and functions:

 

By implanting and eating into the ovaries, endometriosis can reduce the supply of eggs.  Antral follicle counts (AFC) and anti-Müllerian hormone (AMH) levels are two frequently used indicators of ovarian reserve, and recent studies have suggested that patients with endometriosis have a reduced ovarian reserve, even before it occurs. make attempts to clear endometriosis.

Surgery to remove endometriosis in the ovaries can also further reduce the ovarian reserve.  Endometriosis sticks closely to normal ovarian tissue and some of the normal ovarian tissue is inevitably removed during removal of endometriosis from the ovary.  Several studies have documented the reduction in AMH levels after elimination of endometriosis.  For patients with good ovarian reserve, these changes may not affect the likelihood of having a successful pregnancy, but for patients with already low reserves, particularly those who will need  IVF  , surgery can have a significant negative impact.

Reduced quality

Also, endometriosis can create an environment that can worsen egg quality.  A meta-analysis of 22 studies and 6,760  patients with  IVF  showed that endometriosis patients have  rates of  fertilization  plus  low and lower implantation rates per embryo than other patients (in this case, those with blocked tubes).

Additionally, a small study shows that embryos created from donor eggs with endometriosis are much less likely to implant than embryos created from donor eggs without endometriosis.

 

Fallopian tube

Endometriosis and related scars around the fallopian tubes can create blockages or abnormal functions that prevent the egg or embryo from moving up the tube or the sperm from moving upward.  This can prevent the sperm from fertilizing the egg or, if fertilization occurs, impede the movement of the resulting embryo through the tube, increasing the risk of a tubal (ectopic) pregnancy.  In a recent study of more than 14,000 women, women with endometriosis were 2.7 times more likely to have an ectopic pregnancy than women without endometriosis.  Although the absolute numbers are small, ectopic pregnancies can be very dangerous.

Uterus

When endometriosis cells colonize other organs, they cause inflammation.  Since the uterus is part of a larger reproductive ecosystem, when other organs become inflamed, so does the uterus.  This can affect the uterus' ability to allow an embryo to implant and receive nourishment.  An interesting design study showed that donor embryo recipients with endometriosis were at least 20% less likely to have embryo implants than donor embryo recipients who did not have endometriosis.

Sperm

Regardless of where endometriosis exists, it creates inflammation, and if sperm swim near the region of inflammation, its  motility  (ability to swim) and its function may be affected.  The percentage of sperm with DNA damage doubles after exposure to pelvic fluid from patients with endometriosis compared to sperm exposed to pelvic fluid from women without endometriosis.  

Additionally, women with Stage I or II endometriosis have been found to have significantly lower fertilization rates after conventional IVF, although this may also be due to egg factors.