When does mother-to-child transmission of hepatitis C virus occur?

Objective: To investigate when hepatitis C virus (HCV) infection from mother to child occurs, and evaluate possible associated factors. Design: Prospective cohort study. Patients: Fifty four HCV infected children tested within three days of birth and their mothers. Main outcome measures: HCV RNA polymerase chain reaction (PCR) results. Results: Seventeen of the children (31%, 95% confidence interval 19% to 46%) were positive in the first 3 days of life and could be assumed to have acquired infection in utero. Testing PCR positive was not associated with sex (53% v 49% boys; p  =  0.77) or mode of delivery (29% elective caesarean section in both groups; p  =  0.98). Children with evidence of intrauterine infection were significantly more likely to be of lower birth weight and infected with genotype 1 (58% v 12%, p  =  0.01). Although a higher proportion of infants born to HCV/HIV co-infected women were PCR positive in the first 3 days of life, this difference did not reach statistical significance; excluding infants born to co-infected women did not affect the results. Thirty seven of the children (68%) were negative in the first 3 days of life, 27 of whom were positive when tested again at 3 months, and nine were first PCR positive after 3 months (one child had no further tests). Conclusions: These results suggest that at least one third and up to a half of infected children acquired infection in utero. Although postpartum transmission cannot be excluded, these data suggest that it is rare. The role of HCV genotypes in the timing and mechanism of infection should be explored further.