The level of passive neonate protection against HSV depends on the transplacentally acquired neutralized HSV antibodies' titer. In this study we investigated the anti HSV antibodies' transplacental passage in a group of women who delivered vaginally and pregnant women who had cesarean section, with the aim of examining the influence of the mode of delivery on the level of passive immunity to HSV. Serologic examination was performed in a group of 102 women who delivered vaginally and 80 pregnant women who had cesarean section, using the test of microneutralization. The titer of anti HSV type 1 and anti HSV type 2 antibodies in the mothers' and cord blood was determined and compared. The cord serum neutralizing HSV type 1 antibodies' titer, was twice higher as compared to those in mothers blood in 60.7% of paired sera in the group of women who delivered vaginally. The cord serum anti HSV type 1 titers were twice as high as compared to those in mothers' blood only in 15.5% of paired sera in group of pregnant women who had cesarean section. In the cases when cesarean section was performed, our results showed the lack of anti HSV type 2 antibodies in 15% of cord sera, even though the mothers' sera were anti HSV type 2 positive. The results of this study point to the possibility that antibody transfer through the placenta is an active and selective process that depends also on the mode of delivery: there are lower levels of HSV neutralizing antibodies in the cord sera of infants whose mothers had cesarean section compared to those who delivered vaginally.