Synergistic Effects of Endometriosis and Preeclampsia on Adverse Pregnancy Outcomes: A Population Database Cohort Study

STUDY OBJECTIVE: Endometriosis affects approximately 10% of women of reproductive age and is associated with an increased risk of adverse pregnancy outcomes. However, the relationship between preeclampsia, endometriosis, and subsequent adverse pregnancy outcomes remains unclear. The purpose of our study was to evaluate the association between endometriosis and preeclampsia, and to assess their combined effect on preterm birth and cesarean delivery. DESIGN: Women with diagnoses of endometriosis and preeclampsia were identified using ICD-9 codes. A multivariable logistic regression model was used to estimate adjusted odds ratios (aORs) for maternal age, race, insurance status, smoking, obesity, chronic hypertension, anxiety, depression, gestational hypertension, and gestational diabetes. Additionally, we evaluated the combined effects of endometriosis and preeclampsia on preterm birth and cesarean delivery. SETTING: The Healthcare Cost and Utilization Project - Nationwide Inpatient Sample (HCUP-NIS) 2004 to 2014. PATIENTS: A total of 9,082,246 pregnant women aged 15 to 49 years. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: There were 652,354 (7.18%) patients who had preterm delivery and 2,936,759 (32.3%) had cesarean delivery. Endometriosis was diagnosed in 5,634 (0.1%), preeclampsia in 326,195 (3.6%), and both conditions in 318 (0.003%) patients. Women with endometriosis alone had 56% higher odds of preeclampsia (aOR = 1.556, 95% CI: 1.414-1.712). When evaluating the association with preterm birth, endometriosis alone increased the odds (aOR = 1.556, 95% CI: 1.414-1.712), preeclampsia alone quadrupled the odds (aOR = 4.08, 95% CI: 4.04-4.12), and the combined presence of both conditions further elevated the risk (aOR = 5.76, 95% CI: 4.41-7.52). Regarding cesarean delivery, the odds were also heightened: endometriosis alone had an aOR of 6.13 (95% CI: 5.73-6.56), preeclampsia alone had an aOR of 2.45 (95% CI: 2.43-2.47), and the combined exposure resulted in an aOR of 12.55 (95% CI: 8.82-17.87). CONCLUSION: Endometriosis is associated with preeclampsia, and when both conditions co-occur, the likelihood of preterm birth and cesarean delivery is markedly amplified.