Subinvolution of the placental site as an anatomic cause of postpartum uterine bleeding: a review.

Context: Subinvolution of the placental site is an anatomic cause of delayed postpartum uterine bleeding that may be underrecognized by general surgical pathologists.
Objective: To review the physiology of uteroplacental arterial development and normal postpartum involution, and to present the characteristic clinical and histopathologic features of subinvolution.
Data Sources: Literature review (MEDLINE via PubMed and Ovid) regarding the pathology and pathophysiology of placental site subinvolution. Review of the clinical and pathologic characteristics of our own institution's previously diagnosed cases of subinvolution from hysterectomy and endomyometrial curettage specimens.
Conclusions: Surgical pathologists must be aware of the cardinal histopathologic findings of subinvolution, and this diagnosis must be considered in every postpartum curettage or hysterectomy specimen presented to the surgical pathologist. Subinvolution of the placental site is an important diagnosis, as this process implies an idiopathic cause, rather than an iatrogenic cause, of postpartum uterine bleeding. The etiology of placental site subinvolution remains poorly characterized.