Prospective Reevaluation of Risk Factors in Mother-to-Child Transmission of Hepatitis C Virus: High Virus Load, Vaginal Delivery, and Negative Anti-NS4 Antibody

Of 21,791 pregnant women screened in Tottori Prefecture, Japan, 127 (0.58%) were positive for anti—hepatitis C virus (HCV) antibody and 84 (0.39%) were positive for HCV RNA. Of 84 children followed up for at least 6 months, 7 (8%) were infected. All of them were born to 26 mothers with a high virus load (HVL; ⩾2.5 × 106 RNA copies/mL [27%]), compared with 0 of 58 children born to non-HVL mothers (P < .001). Because all the infected children were vaginally delivered, the infection rate among 16 vaginally delivered children born to the HVL mothers was as high as 44%. The prevalence of anti-NS4 antibody in the mothers with an infectious HVL was significantly lower than that in the mothers with a noninfectious HVL (P = .048). Analysis of our results suggests that maternal HVL, vaginal delivery, and negative anti-NS4 antibody are significant risk factors for the mother-to-child transmission of HCV.