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

OBJECTIVE: 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. DESIGN: Multicenter retrospective cohort study. PATIENTS: Deliveries by 368,935 women (377,338 infants) from 1999 through 2016. EXPOSURE: 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. RESULTS: 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. CONCLUSION: Pregnant women with endometriosis had higher risks of preterm birth and other poor pregnancy outcomes than women without endometriosis.