Secondary Postpregnancy Hemorrhage: Guide for Diagnosis and Management.

Secondary postpregnancy hemorrhage (PPH) is increasing in incidence, especially in developed countries such as the United States. PPH occurs after 24 hours and up to 12 weeks in the postpregnancy period and may be associated with significant maternal morbidity. Common causes of secondary PPH are subinvolution of the placental site (SIPS) and retained or residual products of conception (RPOC). Other less common and rare causes include bleeding diathesis, endo(myo)metritis, gestational trophoblastic disease, and vascular anomalies such as congenital arteriovenous malformation (AVM), iatrogenic arteriovenous fistula, or pseudoaneurysm. A common finding encountered during imaging evaluation of secondary PPH is increased vascularity in the myometrium deep to an implantation site, termed enhanced myometrial vascularity (EMV). EMV typically represents the physiologic reversion of the uterus back to its prepregnancy state. The appearance of EMV varies from mild to marked and is also associated with SIPS and RPOC. Interpretation or reporting of EMV as an AVM or other rare uterine vascular anomaly may lead to unnecessary testing and overtreatment. The authors review placental physiology, describe the causes of secondary PPH and their imaging appearances, and present an algorithm to assist the radiologist in diagnosis of this important condition and management options. ©RSNA, 2025 Supplemental material is available for this article. See the invited commentary by Gomez in this issue.