Research on the mother-to-infant transmission of hepatitis C virus

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The major route of infection by hepatitis C virus(HCV) has been blood transfusion in recent years in Japan. Mother-to-infant transmission of this virus is suspected as one of the most important routes of natural infection, but its frequency nor factors affecting this infection are not known. Since the carrier status develops even when adults are infected by HCV, which is rare by hepatitis B virus, the retrospective study of the families of HCV carriers cannot elucidate the above mentioned problems. In this research we conducted a prospective follow-up study of the infants born to the HCV carrier mothers found by screening of pregnant women.Pregnant women in six different districts of Japan were screened for serum antibody for HCV (second generation, anti-HCV) and if it was positive the serum HCV RNA was examined using polymerase chain reaction. 0.45 to 1.5% (mean 1%) of the pregnant women were positive for anti-HCV, and 71 to 76% of anti-HCV positive women were also positive for serum HCV RNA.Infants born to HCV RNA positive pregnant women were followed after birth with intervals of one to three months for more than one year after birth, examining their sera foranti-HCV, HCV RNA, as well as transaminase levels. Until now 174 infants had been followed for more than six months after birth, and six (3.4%) of them developed chronic HCV carrier status, and seven other infants showed transient infection by HCV before six months of age.Close evaluation of various factors regarding mother-to-infant infection disclosed that 1) the mothers of HCV infected infants showed higher serum HCV RNA level, and 2) most of these mothers showed apparent elevation of serum transaminase levels, but 3) no difference of infection rate was found between HCV genotypes, nor 4) between breast-fed and bottle-fed infants.