Studies Clarify Risk Factors For Mother-to-child Transmission Of Hepatitis C Virus

One study found that infant girls are twice as likely to be infected as infant boys. Both studies provide new information with which to counsel pregnant women infected with HCV. Taken together, the two new studies expand upon preliminary data from smaller studies of mother-to-child transmission of HCV.

The larger of the two studies, conducted by the European Paediatric Hepatitis C Virus Network, involved 1,479 mother-and-child pairs enrolled at 33 centers in Italy, Spain, Germany, Ireland, the United Kingdom, Norway, and Sweden. The other study, by Eric E. Mast, MD, MPH, of the U.S. Centers for Disease Control and Prevention and colleagues, followed 244 infants born to infected mothers in Houston and Honolulu.

The finding of gender differences in HCV infection was reported by the European authors, who hypothesized that their result may reflect hormonal or genetic differences between men and women in susceptibility or response to infection. Other risk factors significantly associated with transmission were the time in labor (a risk factor in both studies) and use of internal fetal monitoring devices (a risk factor in the U.S. study only).

Although breastfeeding is a known risk for HIV transmission, both studies found it was not associated with transmission of HCV. The European study also found that caesarean section delivery, infant prematurity, and maternal history of injection drug use were not associated with HCV transmission.

The overall rate of transmission of the virus from infected mother to child was 6.2 percent in the European study and 3.6 percent in the U.S. study.

"Our results strongly suggest that women should not be offered an elective caesarean section or discouraged from breastfeeding on the basis of hepatitis C infection alone," said Pier-Angelo Tovo, MD, the lead author of the European study.

"Our findings support existing recommendations to avoid internal fetal monitoring and prolonged labor…in infected women," wrote the U.S. authors.

In an accompanying editorial, R. Palmer Beasley, MD, of the University of Texas at Houston, emphasized the European study's novel finding of a gender difference in transmission rates and suggested that higher HCV rates in female newborns may be due to excess mortality in infected males in utero. "Overall, the observation of higher hepatitis C virus infection rates in female infants is in accord with recent observations of similar excesses in HIV infection of female infants," Dr. Beasley said.