Placental pathology

The placenta is a unique organ, given that it resides at the interface between two human beings – the mother and the fetus. Additionally, it changes throughout gestation in such a dynamic way that identifying the normal histology can be a challenge in and of itself. This article summarizes the most common pathologic changes in the placenta, devoting the greatest amount of information to the inflammatory disorders and abnormalities of fetal and maternal perfusion. These include acute chorioamnionitis and funisitis/chorionic plate vasculitis, chronic villitis, and changes secondary to maternal vasculopathy and fetal thrombosis. Less common abnormalities that are either often seen or important to identify are described, and the findings in the most common perinatal infections are summarized. Finally, the clinical associations of the placental pathologic findings are described. The intent is to provide a framework for diagnosing common placental abnormalities, and references are provided for further reading.