Higher risk of hepatitis C virus perinatal transmission from drug user mothers is mediated by peripheral blood mononuclear cell infection.

Maternal injection drug use and peripheral blood mononuclear cell infection by hepatitis C virus are important risk factors for perinatal transmission of the virus. The aim of present study was to evaluate the independent association of these two factors on perinatal transmission. Forty-eight consecutive mothers who transmitted infection to their offspring and 122 consecutive mothers who did not, together with their children, were examined. Both maternal injection drug use and peripheral blood mononuclear cell infection were significantly more frequent in infected than in uninfected children (respectively P = 0.04; odds ratio 2.33, 95% confidence intervals 1.02-5.42 and P < 10(-6); odds ratio and 95% confidence intervals not calculable due to zero values). Multivariate analysis confirmed the link between maternal peripheral blood mononuclear cell infection and perinatal transmission (P < 10(-6); odds ratio and 95% confidence intervals not calculable due to zero values) but no association was found with maternal injection drug use. The high risk of perinatal transmission found in injection drug use mothers is dependent on maternal peripheral blood mononuclear cell infection by hepatitis C virus. Peripheral blood mononuclear cell infection represents one of the most important risk factors for hepatitis C virus perinatal transmission.