Maternal Endometriosis Associated With Higher Increase in Birth Defect Risk: Study

A pregnant woman holds her stomach in a file image. Ian Waldie/Getty Images

Women suffering from endometriosis are at a greater risk of delivering babies with birth defects, new research suggests.

The study, released this week by the Canadian Medical Association Journal (CMAJ), examined data from more than 1.4 million births in Ontario over a span of about 15 years, from April 7, 2006, to March 31, 2021.

The research found that 6.3 percent of babies born to mothers with endometriosis had a birth defect, compared to 5.4 percent of those born to women without the chronic gynecological disorder. Over the study period, researchers examined 33,619 births to women with endometriosis and 1,426,835 births to women without the condition.

The researchers concluded that endometriosis was associated “with a higher risk of any congenital anomaly.” A congenital anomaly is a structural or functional abnormality that develops before birth.

The study found women with endometriosis are more likely to deliver a baby with cardiovascular, gastrointestinal, genital, or musculoskeletal birth defects, which may include tumours.

There was also a slight increase in the risk for pulmonary artery stenosis, a narrowing of the arteries that carry blood from the heart to the lungs, forcing the heart to work harder to pump blood. Cleft palate and hypospadias, a defect in the male genitals, were also more common.

Endometriosis and Fertility

Endometriosis is a chronic condition that causes tissue similar to the uterine lining to grow outside the uterus.

While the exact cause of endometriosis is unknown, those who have a close relative with the condition have a higher chance of having it too, according to the Endometriosis Network Canada.

Nearly 2 million Canadian women suffer from the disease, which can cause pelvic pain, infertility, and inflammation. There is no cure, but the condition can be managed with medication, hormonal therapy, and excision surgery to remove lesions.

The research indicated that women diagnosed with endometriosis had a higher average age at delivery—33.4 years—than women without the condition. They were less likely to fall within the lowest income quintile, yet more likely to experience subfertility and to achieve conception through fertility treatments.

Women with endometriosis who underwent fertility treatments faced a higher risk of adverse outcomes, the study authors wrote. The main factor was the endometriosis itself, the study added, noting that fertility treatments like IVF played a minimal role in increasing the risk of birth defects.

Subfertility, along with less invasive fertility treatments such as ovulation induction and intrauterine insemination, did not influence the relationship between endometriosis and anomalies, the authors said. They said women who conceived without invasive fertility treatments may have had milder cases of endometriosis.

Endometriosis Care

An article published in the same issue of CMAJ referenced the study, noting that the discovery of a heightened risk of birth defects in infants born to patients with endometriosis underscores the necessity for improved diagnosis and treatment of the condition.

The article by Dr. Olga Bougie, University of Toronto associate professor in the department of obstetrics and gynaecology, and CMAJ deputy editor Dr. Catherine Varner described endometriosis as a condition that remains under-recognized and under-treated in Canada.

“Patients with endometriosis, or symptoms suggestive of the condition, often show a pattern of fractured care across multiple health care settings, including emergency departments, primary care, and subspecialty clinics such as pediatrics, gastroenterology, urology, and chronic pain,” they wrote.

“Their symptoms are frequently minimized or dismissed, which contributes to delays in both diagnosis and care, and patient mistrust.”

The article advocates for a community-of-practice framework for the management of endometriosis, emphasizing a need for support for primary care physicians in diagnosing and handling uncomplicated cases.

Within this same framework, patients with suspected complex or high-risk endometriosis can be identified at an early stage and directed to health centres with expertise in advanced surgery and multidisciplinary teams, the doctors wrote.