[A molecular epidemiology study on risk factors and mechanism of HBV intrauterine transmission].

OBJECTIVE

To clarify the risk factors and mechanism of HBV intrauterine infection by molecular epidemiology method.

METHODS

We performed a case-control study. 402 HBsAg-positive pregnant women and their infants were collected as subjects. 15 infants infected by HBV intrauterine transmission were selected as case group and others as controls. Besides, HBsAg titer in 182 maternal sera and HBV DNA concentration in 185 maternal sera were determined. To identify the HBV infection in the placentas, immunohistochemistry stain and HBV DNA hybridization in situ were conducted. The data from both laboratory and epidemiological fields were analysed.

RESULTS

The findings indicated that the positiveness of HBeAg in mother's sera (OR = 17.07) and the history of threatened premature labour (OR = 5.44) were the main risk factors. Intrauterine transmission was significantly related to HBsAg titers and HBV DNA concentration in mother's sera (P = 0.01). The results of immunochemistry stain and HBV DNA situ in hybridization in the placentas from 101 full-term pregnancy women showed that HBV infection rates had a decreasing trend (P = 0.0009) from mother's side to fetus's in placenta and there was a significant association between HBV intrauterine transmission and HBV infection in villous capillary endothelial cells in placenta (OR = 18.46, P = 0.0002).

CONCLUSION

There might be a "cellular transfer" of HBV infection in the placenta. With regard to the mechanism of HBV intrauterine transmission; there are two transmission routes, namely, hemagenous route and cellular route.