Association Between First-Trimester Bleeding and Retained Placenta Requiring Dilatation and Curettage

Objective: Early subchorionic hemorrhage may lead to a disruption in the placental-uterine matrix, which may result in an adherence of the placenta to the endometrium. We evaluated the effect of a first-trimester bleed on the need for a post-vaginal delivery dilatation and curettage (D&C) for removal of retained placenta. Methods: We conducted a case-control study at a tertiary care centre between 2012 and 2016. Patients identified through medical records as having required a post-vaginal delivery D&C for retained placenta were considered cases and were matched 1:5 with patients delivering vaginally within 1 week who did not require a D&C. History of first-trimester bleeding and subchorionic hemorrhage were identified through chart review. Conditional logistic regression analyses estimated the effect of a first-trimester bleed on the requirement for D&C for retained placenta. Models were adjusted for maternal age and previous uterine surgery. Results: There were 68 cases of retained placenta requiring D&C, for an estimated 3 in 1000 deliveries. Patients requiring D&C were slightly older than controls but were otherwise comparable with respect to baseline demographic characteristics. In adjusted analyses, patients who required a postpartum D&C were more likely than controls to have had a first-trimester bleed at 11.8% and 0.6%, respectively (OR 25.3; 95% CI 4.7-135.4, P < 0.001). Postpartum D&C for retained placenta was associated with postpartum hemorrhage, need for blood transfusion, and manual removal of placenta. Conclusion: First-trimester bleeding should be considered a high-risk determinant for post-vaginal delivery D&C for retained placenta and for severe postpartum hemorrhage.