Endometriosis and preterm delivery: Should there be a warning?


There are a lot of things women can worry about during pregnancy, but a new study suggests that some mothers need even more warnings than others.

Endometriosis is a condition that affects up to 10% of women in their reproductive years. Even when they are able to overcome the obstacles of this condition and become pregnant, researchers now say they may need to worry about an increased risk of preterm delivery. Other experts, however, aren’t so sure there is enough evidence to warrant these red flags.

A new study, published in Reproductive Science, set out to determine whether there is enough link between endometriosis and preterm birth to warrant increased education about the risks for mothers with the condition.1 After a retrospective review of 3 studies involving more than 10,000 women, researchers concluded that there was, in fact, enough of an increased risk of premature delivery among pregnant women with endometriosis to justify bigger warnings.

Laura E. Riley, MD, obstetrician and gynecologist in chief at NewYork-Presbyterian Hospital/Weill Cornell Medical Center, chair of the Department of Obstetrics and Gynecology at Weill Cornell Medicine in New York City, New York, and Contemporary OB/GYN® editorial advisory board member, says while there is some plausibility to the theories presented in the paper, there are still more questions than answers.

“It is unclear given the heterogeneity of the populations—despite statistical methods to account for these biases—some potentially important biases will remain,” says Riley. “Thus, it leads to questioning association versus cause and what aspect of the association is strongest.”

Endometriosis and pregnancy

Endometriosis is a condition that leads to the formation of stroma and glandular tissue outside of the uterus. This estrogen-dependent condition occurs in 6% to 10% of women, mostly among those who are in their reproductive years, according to the study.

There’s a number of problems that can arise from the displacement of tissue that occurs in endometriosis, including:


Scar tissue formation


Chronic pelvic pain





Perhaps one of the greatest concerns women with this condition have, though, is the impact it can have on their fertility. Endometriosis can reduce fertility in several ways, the report suggests. It can impair ovarian health and reserve, as well the implantation process. Endometriosis can even affect the interactions between sperm and egg. According to the research team, roughly 35% to 50% of women who experience infertility have also been diagnosed with endometriosis. Assisted reproduction and other efforts to increase fertility have helped reduce this number, but this brings up a new concern—how will endometriosis affect the health of a pregnancy?

Is there reason for worry?

Preterm delivery appears to be the biggest issue linked to endometriosis during pregnancy, the researchers note. The change in the uterine wall from a state of rest to a state of activity during labor is believed to be the catalyst in endometriosis-related pregnancy complications, according to the report.

The research team suggests that preterm labor in pregnant mothers with endometriosis may be triggered by the imbalance between anti-inflammatory and proinflammatory pathways that begins the labor process. While this imbalance is the natural order of things, the study suggests that women with endometriosis are actually overachievers when it comes to these pathways. A hyperexpression of these inflammatory mediators—along with changes in estrogen levels, oxidative stress, gene expression, and progesterone resistance—creates a perfect storm that can launch preterm labor.

Gaining a better understanding of how endometriosis can impact the chances of prematurity is important because of the developmental fallout that can follow infants who are born prematurely, the authors warn.

Studies that have investigated the link between prematurity and endometriosis in the past have been somewhat inconclusive, but the authors of the new report say there is at least enough data to support more concern over this condition as a risk factor for preterm delivery.

Additionally, the authors note that, at least in theory, more women with endometriosis are overcoming infertility and achieving pregnancy with various fertility treatments—which also carry a higher risk of preterm delivery.

Question remain

Although there are still questions about a causative relationship between endometriosis and preterm delivery, the study authors say that at the very least, women should be warned about possibility that these risks may be increased with endometriosis. The paper also calls for more studies on possible interventions that could mitigate this risk.

Generally speaking, education is never a bad thing. However, Riley cautions that educating women with endometriosis on mere generalities involving the potential pregnancy risks their condition may lead to seems unhelpful.

“We don’t know what, if any, interventions can change the risk,” Riley adds. “Education about the disease at the time of diagnosis…is important but causing women to worry more about a risk we can’t yet define or intervene on needs to be done carefully.”

Riley suggests that more research should be done before women with endometriosis are specifically cautioned any differently than other pregnant mothers about the risks of preterm labor.


  1. Bonuccelli GA, Negrini R, da Silva Ferreira RD. Premature Birth in Women with Endometriosis: a Systematic Review and Meta-analysis. Reprod Sci. 2022 Jan;29(1):250-259. doi: 10.1007/s43032-021-00712-1. Epub 2021 Aug 23. PMID: 34426947.
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