Mother-to-child transmission of hepatitis C virus: evidence for preventable peripartum transmission

Background Little information is available about the timing of mother-to-ch ild transmission of hepatitis C virus (HCV), and no interventions to decrea se transmission rates have been identified. We examined the effect of risk factors, including mode of delivery, on the vertical transmission rate. Methods Data from HCV-infected women and their infants from three hospitals in Ireland and from a British Paediatric Surveillance Unit study of infant s born to HCV-infected mothers were used to estimate the vertical transmiss ion rate and risk factors for transmission. We used a probabilistic model u sing methods that simultaneously estimated the time to HCV-antibody loss in uninfected infants and the diagnostic accuracy of PCR tests for HCV RNA. Findings 441 mother-child pairs from the UK (227) and Ireland (214) were in cluded. 50% of uninfected children became HCV-antibody negative by 8 months and 95% by 13 months. The estimated specificity of PCR for HCV RNA was 97% (95% CI 96-99) and was unrelated to age; sensitivity was only 22% (7-46) i n the first month but rose sharply to 97% (85-100) thereafter. The vertical transmission rate was 6.7% (4.1-10.2) overall, and 3.8 times higher in HIV coinfected (n=22) than in HIV-negative women after adjustment for other fa ctors (p=0.06). No effect of breastfeeding on transmission was observed, al though only 59 women breastfed. However, delivery by elective caesarean sec tion before membrane rupture was associated with a lower transmission risk than vaginal or emergency caesarean-section delivery (odds ratio 0 [0-0.87] , p=0.04, after adjustment for other factors). Interpretation The low sensitivity of HCV RNA soon after birth and the find ing of a lower transmission rate after delivery by elective caesarean secti on suggest that HCV transmission occurs predominantly around the time of de livery. If the findings on elective caesarean section are confirmed in othe r studies, the case for antenatal HCV testing should be reconsidered.