Health Conditions Connected to Endometriosis

Reviewed by: HU Medical Review Board | Last reviewed: June 2018

Endometriosis has been linked to a variety of complications and comorbidities. Comorbidities are conditions that co-occur or co-exist together at the same time. As an example, if a woman with endometriosis also has multiple sclerosis (MS), these would be considered comorbid conditions. Comorbidities may arise by chance, or they may be related to one another. Some conditions carry a higher chance of developing specific comorbid conditions because the mechanisms behind the conditions are similar, or because they share similar risk factors. Common complications and comorbid conditions associated with endometriosis include, but are not limited to, the following.

Infertility and pregnancy complications

Infertility is the inability to get pregnant or carry a baby to term, however, endometriosis does not always cause complete infertility. In some cases, endometriosis may decrease a woman's chances of getting pregnant, however, pregnancy is still possible. In other cases, a woman's fertility may not be affected at all. In addition to having an association with infertility, research suggests that women with endometriosis may also have a higher risk of developing pregnancy-related complications. These complications include, but are not limited to, delivering preterm, miscarriage, ectopic pregnancy, undergoing a caesarean section (C-section), experiencing pre-eclampsia (high blood pressure and protein in the urine that develops later in pregnancy), placental complications, uterine rupture, bowel perforation, and bleeding during or after birth.1-5

Since endometriosis commonly affects the female reproductive system and structures surrounding the uterus, it makes sense that fertility and pregnancy may be affected. Common theories as to why fertility and pregnancy may be affected by endometriosis include scarring that blocks the fallopian tubes or that has impacted the structure of key reproductive organs, immune system-related issues that cause the body to mistakenly attack a developing fetus, and developmental anomalies or malformations of the uterus or other structures in the female reproductive system (such as developing an abnormally shaped uterus).2-6

Scar tissue and adhesions

In addition to forming on the skin, scars and scar tissue can form on the inside of the body as a result of inflammation, trauma, or other damage. Over time, internal scar tissue can build up and form fibrous bands called adhesions. Adhesions can cause severe pain as well as structural damage. As an example, adhesions can form on the surface of an organ and connect it to another structure in the body, such as an ovary being bound to the pelvic wall.

Scar tissue often forms in areas that are inflamed. Since endometriosis is a condition that involves constant inflammation, scar tissue is likely to form. Additionally, as endometrial-like tissue is thickening and breaking down regularly in places where blood cannot escape, scar tissue may also be regularly forming as the body attempts to heal from these ever-changing lesions. Endometriosis-related scarring may affect fertility, as it could impact the structure and function of the ovaries, block the fallopian tubes, or affect other female reproductive structures. Additionally, adhesions can form as a result of endometriosis-related surgical procedures, causing further complications.7-10


The association between endometriosis and cancer has been of interest to experts for decades. Although research into this potential relationship has been performed for some time, much more needs to be investigated in order to better understand the many dynamics at work. It is important to note, however, that malignant transformation of endometriosis, otherwise known as cancer development related to endometriosis lesions, is extremely rare. This transformation has only been reported in roughly 1% of all cases of endometriosis, and is thought to only occur in atypical lesions.11-13 A common theory is that the cells that make up these atypical endometriosis lesions may have some of the same genetic markers or genetic mutations that cancer cells have.11

Outside of direct transformation some experts have theorized that the association between certain cancers and endometriosis may be due to shared risk factors, as well as endometriosis creating an environment suitable for cancer growth. Of the 1% of endometriosis cases that have malignant transformation, 80% of these result in a type of ovarian cancer. Other cancers that may have an association with endometriosis in general are breast cancer, colorectal cancer, endometrial cancer, and non-Hodgkin lymphoma, however, much more research is needed to investigate these associations as well.11,14

Anxiety and depression

Anxiety and depression are two types of mental health conditions. Mental health conditions include a wide variety of disorders that affect the way a person feels, thinks, or behaves. Anxiety, or anxiety disorder, occurs when an individual's normal, healthy anxious feelings continue to grow, develop, and worsen to the point where their normal daily activities and functioning are negatively impacted. Depression involves experiencing a depressed, downtrodden, or sad mood for an extended period of time. Feelings of depression are similar to feelings of sadness; however, they are generally more intense and do not go away. Depression can impact an individual's desire to take part in activities they once enjoyed and can negatively affect self-esteem and self-worth.15,16

The association between endometriosis and the development of mental health conditions like anxiety and depression is one that is actively being investigated by experts in the field. Several studies have shown that endometriosis, and its related symptoms and experiences, can lead to impaired mental health and a decreased quality of life. This association has been predicted to be stronger in women who lack an understanding partner or support system, as well as in those who experience chronic and severe symptoms.17-19

Autoimmune conditions, allergies, and fibromyalgia

Autoimmune conditions and allergies are both related to the immune system. Autoimmune conditions occur when the body's natural defense, the immune system, mistakenly attacks itself. Conversely, allergies are characterized by the body's overreaction of the immune system against non-threatening substances. In contrast, individuals who have fibromyalgia experience widespread musculoskeletal pain, the hallmark symptom of the condition, which has not yet been connected to the immune system. This pain can be described as constant and like a dull ache on both sides of the body, above and below the waist, and its exact cause has not yet been determined.

The exact mechanism by which endometriosis is associated with autoimmune conditions, allergies, and fibromyalgia is not well understood, however, many studies have suggested that a correlation exists. Since a proposed cause of endometriosis is an altered or faulty immune response that allows endometrial tissue to grow in other places within the body, some researchers suggest that this may be the key to the relationship between endometriosis and autoimmune conditions and allergies. As far as endometriosis and fibromyalgia, this link is even less understood. Across many studies it has been apparent that women with endometriosis more commonly have co-occurring fibromyalgia than women without endometriosis, however, the reason for this is unclear. One potential hypothesis is that the chronic pain experienced by women with endometriosis may be a precursor to, or trigger for, fibromyalgia.20

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