The association of endometriosis with placenta previa and postpartum hemorrhage: a systematic review and meta-analysis

OBJECTIVE: This study aimed to review the effect of endometriosis on the prevalence of placenta previa and postpartum hemorrhage in pregnant patients and the surgical outcomes of pregnant patients with endometriosis developing placenta previa. DATA SOURCES: In compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic review of the literature was conducted on December 31, 2020, using PubMed, Scopus, and the Cochrane Library. STUDY ELIGIBILITY CRITERIA: Comparative studies between pregnant women with and without endometriosis and studies that investigated the surgical outcomes of patients with and without endometriosis developing placenta previa were included. METHODS: Here, 2 reviewers independently screened the titles and abstracts, completed data extraction, and assessed the reporting quality using the Risk of Bias in Nonrandomized Studies of Interventions tool. RESULTS: Overall, 19 studies (from 2010 to 2020) met the inclusion criteria (98,463 pregnancies with endometriosis and 7,184,313 pregnancies without endometriosis). In the adjusted pooled analysis, endometriosis was associated with a higher rate of placenta previa (adjusted odds ratio, 3.17; 95% confidence interval, 2.58-3.89), whereas the incidence of postpartum hemorrhage was similar between pregnant women with and without endometriosis (adjusted odds ratio, 1.15; 95% confidence interval, 0.99-1.34). When the analysis was restricted to histologically confirmed endometriosis cases, the relationship of endometriosis with placenta previa (adjusted odds ratio, 4.23; 95% confidence interval, 1.74-10.30) and postpartum hemorrhage (adjusted odds ratio, 1.29; 95% confidence interval, 0.50-3.34) was consistent with results from the nonrestricted analysis. There was no study that examined the surgical outcomes of patients with endometriosis developing placenta previa patients. However, there are 3 studies that examined the effect of endometriosis on surgical outcomes during cesarean delivery: 1 study showing that endometriosis was associated with increased intraoperative bleeding during emergent cesarean delivery; the other study showing that endometriosis was associated with an increased incidence of postpartum hemorrhage during cesarean delivery (adjusted odds ratio, 1.1; 95% confidence interval, 1.0-1.2), especially in primiparous women with singleton pregnancies (adjusted odds ratio, 1.7; 95% confidence interval, 1.5-2.0); and another study suggesting a significantly higher rate of hysterectomy (7.1%) and bladder injury (7.1%) in patients with endometriosis than in those without endometriosis. CONCLUSION: Endometriosis can potentially be associated with adverse surgical outcomes during cesarean delivery. Although there is a correlation between endometriosis and increased rate of placenta previa, the surgical outcomes of patients with endometriosis developing placenta previa remain understudied.