Peculiar ultrastructural features allowed the authors to reveal M. Homminis corpuscles in placental tissues of women with genital mycoplasmosis. Mycoplasma was found in the amniotic epithelium, chorionic plate, in the lumen of villous capillaries, this showing possible hematogenic way of the infection from mother to fetus. In the placenta of women with genital mycoplasmosis immunopathological processes develop in association with formation of pathogenic immune complexes (PIC) that are fixing the C₃ complement fraction. Location of PIC on the syncytiotrophoblast membranes and vascular endothelium causes immunological inflammation with the involvement of immunocompetent cells resulting in the destruction of syncytial membranes and membranes of the placental barrier. Damage to the placental barrier membranes promotes the development of placental failure, a complicated course of pregnancy and delivery, deterioration of the state of the fetus and newborn infant.