Endometriosis May Not Cause Preterm Births

By Cari Wade Gervin
Friday, March 25, 2022

New research found no difference in rates of preterm births after adjusting for other risk factors.

woman holding abdomen and cringing in pain

Endometriosis, the painful pelvic inflammatory condition that affects around 1 in 10 women, has long been associated with certain problems during pregnancy, along with reduced fertility. Research to this point has also suggested that it may slightly increase the risk of preterm birth.

However, new research published in February in JAMA Network Open found that women with endometriosis were not more likely to give birth prior to 37 weeks compared to women without the condition. While further research is needed, this could be good news for millions of women.

The Study

Louis Marcellin, MD, PhD, a professor in the Department of Obstetrics and Gynecology at Université de Paris, led the research across seven hospitals in France. A total of 1,351 women with singleton pregnancies were followed during the gestation period, 470 of whom had known endometriosis. Those women were also categorized by the severity of their condition — superficial, ovarian or deep endometriosis.

After adjusting for preterm birth risk factors like maternal age, BMI, country of birth and previous cesarean delivery, along with the severity of endometriosis, the rate of preterm births was consistent across all cohorts. The women with endometriosis had a preterm birth rate of 7.2%, while the control group had a preterm birth rate of 6.0%. Even with deep endometriosis, the preterm rate was 7.4%. There was also no difference found between rates of spontaneous and induced preterm birth.

The Implications

Dr. Marcellin’s findings contradict prior assumptions about endometriosis. He theorizes that this association may partially be due to physician bias.

“Practitioners also often mistakenly designate pregnancies of women with endometriosis as high risk because of (1) available retrospective data on adverse pregnancy outcomes, (2) known rare but potentially catastrophic acute surgical complications during pregnancy that were related to DE (hemoperitoneum, uroperitoneum, intestinal perforation, and uterine rupture), (3) an extensive surgical history, or (4) a lengthy infertility,” Dr. Marcellin writes.

The research suggests that practitioners should monitor patients with endometriosis the same way they would other patients, according to normal pregnancy protocols to prevent preterm birth.

“These results are valuable and comforting,” writes Liisu Saavalainen, MD, PhD, and Oskari Heikinheimo, MD, PhD, both of the Department of Obstetrics and Gynecology, University of Helsinki and Helsinki University Hospital, in an invited commentary for JAMA Network Open. “However, they are also likely to trigger new studies on the pregnancy risks associated with different types of endometriosis. That is good news.”