During prospective epidemiological surveillance cases of pyogenic and septic infections (PSI) in mothers and newborns in two maternity hospitals were studied using standard case definition and leading risk factors of their development were revealed. These factors differed in two hospitals and were connected mainly with high level of patients colonization, contamination of the environment by nosocomial strains of microorganisms, and degree of participation of mother's relatives in delivery. It was shown that permission to relatives for presence on delivery did not influence on the rate of PSI. Specificity of risk factors of PSI in mothers and newborns dictates necessity to determine them in each maternity hospital.