[Placental development and viral infections].

The stages of placental development are briefly described as well as the cellular and molecular mechanisms involved in the immunologic defense systems at the maternofetal interface. Methods available for morphologic studies of placentas with viral infection are reviewed. Routes of transmission of viruses from mother to fetus, as well as the placental lesions seen in viral infections are discussed. Emphasis is put on the value of "oriented" pathologic studies of the placenta whenever viral fetal disease is suspected.