[Influence of single and repeated pregnancies on the incidence of primary tumors induced by SV40 virus in hamsters].

The influence of the single and repeated pregnancies on the SV40-induced carcinogenesis in Syrian hamsters was studied. It was shown that the frequency of the primary tumours in females which become pregnant 1-5 times during the latent period of SV40 carcinogenesis was significantly lower in comparison with virgin females observed in the same experiment. However, these differences apparently had no connection with the immunization of multiparous females with embryonic antigens, as the frequency and the time of appearance of primary tumours in males were the same as in multiparous females.