Studies on the risk factors of intrauterine infection of hepatitis B virus.

In order to elucidate the mechanism involved in HBV intrauterine infection, some risk factors were checked among 22 HBsAg and HBeAg positive carrier mothers. It was found that the HBV intrauterine infection had no correlation with (1) abnormal maternal liver functions, (2) high HBsAg and HBeAg titers or high concentration of HBV-DNA in the maternal serum or (3) HBeAg titer in the cord serum. Four babies were born to mothers with positive symptoms and signs of threatened abortion and/or threatened premature labor during pregnancy. Among them, two babies born at full term were HBV infected cases in utero, whereas the other two babies born within one week after the occurrence of threatened premature labor showed negative HBsAg antigenemia at birth and HBIG was immediately administered and prevented HBV infection. We therefore inferred that placental leakage caused by uterine contraction during pregnancy could cause maternal blood to enter the fetal circulation and cause HBV intrauterine infection. Moreover, even if placental leakage occurs, HBV infection might be prevented by administering HBIG within a week.