Endometriosis and risk of adverse pregnancy outcomes: a retrospective multicenter cohort study

To investigate first, the association between endometriosis and preterm birth; second, the associations between endometriosis and preeclampsia, placenta previa, postpartum hemorrhage, stillbirth, and small-for-gestational-age infants (assessed by birthweight); and third, the risk of these adverse pregnancy outcomes with and without the use of medically assisted reproduction.

Multicenter retrospective cohort study.

Deliveries by 368,935 women (377,338 infants) from 1999 through 2016.

Endometriosis, defined as a single disease entity (endometriosis and/or ademyosis) MAIN OUTCOMES MEASURES: The main outcome was the preterm birth rate (both <37 and <33 weeks). The secondary outcomes were rates of preeclampsia, placenta previa, postpartum hemorrhage, stillbirth, and small-for-gestational-age neonates.

Women in the endometriosis group had more frequent histories of infertility before the included pregnancy (34.7 vs. 5.0%), more hospitalizations during the pregnancy (27.4 vs. 19.8%), and more planned cesarean sections (14.0 vs. 8.7); they more often were nulliparous (51.7 vs. 43.4%). The prevalence of preterm birth at <37 weeks was 11.1% in the endometriosis group and 7.7% in the unexposed group, and for <33 weeks, it was 3.1% and 2.2%, respectively. The adjusted relative risk for confounding factors was higher in the endometriosis than the unexposed group for preterm delivery <37 weeks (1.40, 95% confidence interval, 1.18-1.67) or <33 weeks (1.53, 95% confidence interval, 1.08-2.16). For the secondary outcomes, the adjusted risk ratios for preeclampsia, placenta previa, postpartum hemorrhage, and small-for-gestational-age status of <10th and <5th percentiles were higher in the endometriosis group. The adjusted risk ratios for stillbirth and small-for-gestational-age status of <3rd percentile did not differ between the two groups, and those after stratification by medically assisted reproduction for preterm birth at <37 and <33 weeks did not differ statistically significantly between them, for the secondary outcomes, only the risk of placenta previa was higher in the medically assisted reproduction and non-medically assisted reproduction subgroups.

Pregnant women with endometriosis had higher risks of preterm birth and other poor pregnancy outcomes than women without endometriosis.