The paper reports lethal intrauterine mycoplasmosis in a newborn girl. Her mother suffered from genital mycoplasmosis and had blood antibodies to Myc. Hominis and Ureapl. urealyticum. Most pronounced changes are found in the liver: hepatocyte degeneration and necrosis with PAS- and azur-positive granules in the cytoplasm of hepatocytes and macrophages, lymphohistiocytic infiltration of portal tracts and parenchyma, biliary duct proliferation, cholestases. The lungs: interstitial pneumonia with minimal alteration of the bronchial epithelium. The above spectrum of alterations suggests transplacental contamination. Ganglioneuroblastoma consisting of embryonal neuroblasts found in the adrenals is considered as an independent disease. The first child of this woman died 14-days old and had morphological signs of the intrauterine infection and pronounced liver dysplasia; possible oncogenicity of mycoplasma is discussed.