Endometriosis is when tissue from the lining of the womb is elsewhere in the body. Usually this is behind the womb near the ovaries or Fallopian tubes, but can be found anywhere in the body.

When on a period, spots of endometriosis also become inflamed resulting in pain, or sticking together of tissues causing scar tissue, also known as adhesions.

Endometriosis is linked with pelvic pain, pain during intercourse and fertility problems. No cure has been found for endometriosis and so treatment is focussed on managing the condition.

Diagnosing endometriosis usually requires keyhole surgery to be able to see areas of endometriosis, but can sometimes be seen on ultrasound or MRI scan.

Endometriosis can be described as mild, moderate or severe, but this classification is discouraged by specialists as it doesn’t correspond well with symptoms and is poorly defined by clinicians and researchers. Surprisingly, the extent of endometriosis seen during surgery often doesn’t compare with the severity of symptoms. I have met women have severe endometriosis found during surgery, but experience very little in terms of pain. Then again, others have debilitating symptoms from just a couple of spots.

ASRM Staging

The American Fertility Society (AFS) now known as ASRM (American Society for Reproductive Medicine) endometriosis proposed a staging system to classify the severity and extent of endometriosis. This system is widely used by healthcare professionals to describe the stage of endometriosis based on the location, depth, and extent of endometriotic lesions.

The ASRM endometriosis staging system divides endometriosis into four stages:

Stage 1 (minimal): In this stage, there are a few small lesions or shallow endometriosis implants. There may also be some filmy adhesions or scar tissue.

Stage 2 (mild): In this stage, there are more and deeper implants, as well as more adhesions.

Stage 3 (moderate): In this stage, there are many deep implants and adhesions. There may also be ovarian cysts, known as endometriomas.

Stage 4 (severe): In this stage, there are many deep implants and adhesions, and there may be large ovarian endometriomas. The pelvic organs may also be involved, and there may be evidence of bowel or bladder involvement.

The ASRM endometriosis staging system is useful for guiding treatment decisions and predicting the likelihood of success with different treatment options.

Endometriosis and Fertility

About 30% of endometriosis patients have fertility issues. Endometriosis can affect fertility in several ways:

  1. Adhesions: Endometriosis can cause scar tissue and adhesions to form in the pelvic area, which can interfere with the functioning of the fallopian tubes and ovaries. Adhesions can also prevent the fertilised egg from implanting properly in the uterus.
  2. Ovarian cysts: Endometriosis can cause cysts to form on the ovaries, which can interfere with ovulation and the release of eggs.
  3. Inflammation: Endometriosis can cause inflammation in the pelvic area, which can affect the quality of the eggs and sperm, and can also damage the lining of the uterus, making it difficult for a fertilised egg to implant.
  4. Hormonal imbalances: Endometriosis can cause hormonal imbalances, which can affect ovulation and the menstrual cycle.
  5. Autoimmune factors: Some studies suggest that endometriosis may be associated with autoimmune factors that affect fertility.

What can improve my natural fertility chances with endometriosis?

Research from high-quality studies shows that laparoscopic surgery to excise endometriosis may be beneficial for women with stage 1-2 disease. However, the research is unclear for stage 3-4 disease and those with endometriomas. One research study reviewed women with stage 4 endometriosis and found that pregnancy rates in the two years after surgery for deep endometriosis (stage 4) were 36% in the expectant management group compared with 34% in the surgery group. However, women who had surgery experienced better better symptom control.

Overall, the severity of endometriosis and the location of the endometrial implants can affect fertility. Mild cases may not affect fertility at all, while severe cases may make it difficult or impossible to conceive without medical intervention. However, many women with endometriosis are able to conceive with the help of fertility treatments such as in vitro fertilisation (IVF) or other assisted reproductive technologies.

Endometriosis Fertility Index

The Endometriosis Fertility Index (EFI) is a scoring system used to predict the likelihood of achieving a pregnancy through in vitro fertilization (IVF) for women with endometriosis. It takes into account several factors that may affect fertility, including the woman’s age, duration of infertility, severity and location of endometriosis, and the presence of other fertility-related factors such as male factor infertility.

The EFI is calculated by adding up points assigned to each of the above factors, with a maximum score of 10. A higher score indicates a higher likelihood of achieving pregnancy through IVF. The EFI can be used by doctors to help counsel patients with endometriosis about their chances of success with IVF, and to guide treatment decisions.

Endometriosis and IVF

In vitro fertilisation (IVF) can be an effective treatment for women with endometriosis who are struggling with fertility. During IVF, eggs are retrieved from the ovaries and fertilised with sperm in a laboratory. The resulting embryos are then transferred to the uterus, with the goal of achieving a successful pregnancy.

IVF can be especially helpful for women with endometriosis who have blocked fallopian tubes or other structural issues that are preventing them from conceiving naturally. Additionally, IVF can bypass any potential issues related to the quality or function of the eggs or sperm that may be impacted by endometriosis.

However, even with IVF, endometriosis can still be a factor in fertility. Endometriosis can affect the quality of the eggs or the lining of the uterus, which can make it more difficult for embryos to implant and develop into a viable pregnancy. Additionally, endometriosis can increase the risk of miscarriage.

Overall, the success of IVF for women with endometriosis depends on many individual factors, including the severity of the endometriosis, the age and overall health of the woman.



Matt is an NHS Consultant in Newcastle with over ten years of experience. His PhD research into subfertility and miscarriage involved developing a clinical trial and patient engagement.