Increased risk of mother-to-infant transmission of hepatitis C virus by intrapartum infantile exposure to maternal blood.

Virological and clinical data from 73 hepatitis C virus (HCV)-infected pregnant women who gave birth to 75 children were merged retrospectively, by logistic regression analysis, to investigate risk factors for vertical transmission of HCV. Eighty-two percent of the HCV-infected mothers were HCV-RNA-positive during pregnancy, and 10% were coinfected with human immunodeficiency virus (HIV). Nine children were HCV infected, 1 was HIV infected, but none was HIV-HCV coinfected. Among vaginal deliveries, the mean HCV load of mothers who transmitted HCV to their infants was higher than that of those who did not (8.1 x 10(5) vs. 1.4 x 10(4) copies/mL; P=.056). A reduction in umbilical cord-blood pH (relative risk, 3.9; P=.04) or the occurrence of perineal or vaginal laceration (relative risk, 6.4; P=.028) during vaginal delivery significantly increased the risk of vertical HCV transmission. In conclusion, high maternal viremia, infantile hypoxia, and intrapartum exposure to virus-contaminated maternal blood increased the risk of HCV transmission during vaginal deliveries. Consequently, cesarean section may reduce the risk of vertical HCV transmission in selected cases.