The specific features of microbial contamination during birth were studied in 318 neonates born to mothers with urogenital infection. There was a high rate (as high as 58.2%) of contamination by herpes simplex virus type 2 (HSV-2), cytomegalovirus (CMV), chlamydia, ureaplasma, and mycoplasma in newborn infants with severe intrauterine infection and there was also concurrent isolation of HSV-2 and CMV antigens from neonatal umbilical cord blood and simultaneously from other loci. Chlamydia and ureaplasma were proven to be of etiological importance in the development of intrauterine pneumonias. The high rate of contamination by the aerobic microflora irrespective of the neonatal health status suggests the limited prognostic and diagnostic significance of these pathogens in intrauterine infection.