The role of factor XIIIa in the mesenchymatogenesis of the human placenta: an immunohistochemical analysis.

Human placentas from normal pregnancies [9], interrupted pregnancies due to congenital anomalies of the fetuses [7] and legal abortions [9] were examined immunohistochemically using monoclonal antiserum for factor XIIIa. Hofbauer cells of the chorionic villi were strongly positive for factor XIIIa. Deeper staining in early pregnancy reflects the greater numbers of Hofbauer cells in this period of gestation. Our findings support the hypothesis that the presence of factor XIIIa in the Hofbauer cells promotes the maturation of the chorionic villi.