Fetal infections have high specific gravity in the structure of perinatal diseases and mortality. The gravity of infection processes in pregnancies and degree of fetal pathology are not correlated. Latent asymptomatic forms of pregnant's diseases can often be the cause of the congenital malformations and fetal death. We present here results of the analysis of the frequencies and types of chromosome aberrations in pregnancies with latent infections. The chromosome structure damages, mainly chromatide-type aberrations, were registered with higher frequency in the studied group.