Active hepatitis C virus (HCV) infection during pregnancy is associated with premature birth, and a high viral load increases the risk of vertical transmission, according to findings published in the Journal of Hepatology. However, only a minority of infants born to mothers with HCV are screened for the infection, as is recommended by treatment guidelines.

Previous studies have shown that the mother-to-child HCV transmission rate is around 6%. But the viral load level needed for transmission and the impact of hepatitis C on pregnancy outcomes are not well understood.

Tatyana Kushner, MD, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues conducted a retrospective study to better understand vertical transmission of hepatitis C and its impact on pregnancy outcomes.

Using administrative healthcare data, the team identified 2,170 pregnancies among 1,636 women in Ontario who acquired hepatitis C before pregnancy. In 1,780 of these cases (82%), the women continued to test positive for HCV RNA during their pregnancies, indicating active infection.

Women who tested positive for HCV RNA during pregnancy were more likely to deliver their babies prematurely than those who did not have active HCV infection (18% versus 12%, respectively). The former group was also at greater risk for intrahepatic cholestasis of pregnancy (blocked bile flow) and postpartum hemorrhage. However, women with active HCV infection during pregnancy were less likely to develop gestational diabetes than those who had cleared the virus.

Less than a third (29%) of the newborns born to women with hepatitis C were screened for HCV after birth. Of those who were screened, the mother-to-child transmission rate was 3.5%. Women with an HCV RNA level of at least 6.0 log, or about 1,000,000 copies, had more than a threefold greater likelihood of vertical transmission.

“We found that active hepatitis C during pregnancy increased the risk of pregnancy complications,” wrote the researchers. “We also identified very low rates of testing of infants born to mothers with hepatitis C but found higher rates of hepatitis C transmission to infants in mothers with higher virus levels.”

Click here to read the study in the Journal of Hepatology.

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