Placental pathology in antiphospholipid syndrome.

One of the major targets of antiphospholipid antibodies (aPL) is the placenta, the evolution of which during pregnancy has been well documented. Histopathological findings are related to gestational age, and several physiologic and pathologic alterations that occur during its development. The major findings in placentae from aPL positive patients are thrombosis, acute atherosis, a decreased number of syncytio-vascular membranes, increased number of syncytial knots and obliterative arteriopathy. These findings are not specific to the antiphospholipid syndrome (APS) and sometimes do not correlate with the fetal outcome. Histopathological study of placentae may elucidate mechanisms of action of aPL in fetal loss and other obstetric complications. In addition, it may assist in the investigation of the differential diagnosis between APS and pregnancy-induced hypertension. Immunohistochemical studies of local placental proteins contribute to this differential diagnosis.