Does endometriosis lead to increased risk of adverse pregnancy outcomes?

The majority of women with endometriosis are able to achieve pregnancy, but how the disease impacts risk of adverse pregnancy outcomes is unclear. A recent study in Obstetrics & Gynecology investigated the relationship between laparoscopically confirmed endometriosis and adverse pregnancy outcomes.

The authors used data from the Nurses’ Health Study II, which included 116,429 female US registered nurses aged 25 to 49 at enrollment in 1989. In 2009, participants completed a pregnancy-focused questionnaire and 196,722 pregnancies were reported. Of them, 8,875 (4.5%) pregnancies were identified as being in women with laparoscopically confirmed endometriosis. 

For the study, adverse pregnancy outcomes included spontaneous abortion (fetal loss at < 20 weeks’ gestation), stillbirth (fetal loss at ≥ 20 weeks’ gestation), ectopic pregnancy, gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (preeclampsia or gestational hypertension), preterm birth (PTB), and low birth weight. 

The authors noted that laparoscopically confirmed endometriosis was associated with a greater risk of pregnancy loss in multivariable adjusted models (spontaneous abortion: RR1.40, 95% CI 1.31-1.49; ectopic pregnancy: RR 1.46, 95% CI 1.19-1.80). Supplemental analyses indicated that spontaneous abortion was more likely in pregnancies in women with endometriosis who were younger than age 35 and in first pregnancies. The relation with ectopic pregnancy was stronger for pregnancies in women with endometriosis who did not have a history of infertility. 

Endometriosis was also associated with a greater risk of other adverse outcomes, including GDM (RR1.35, 95% CI 1.11-1.63) and hypertensive disorders of pregnancy (RR 1.30, 95% CI 1.16-1.45). Women with endometriosis also had a 16% higher risk of PTB compared with pregnancies in women without endometriosis. 

The authors believe their findings indicate that women with endometriosis are at increased risk for a number of different adverse pregnancy outcomes. However, more research is needed to better understand the biological factors related to this relationship to better inform screening or preventive interventions.