| [BACKGROUND] Hepatitis B Virus (HBV) intrauterine infection is an important reason for a large number of HBV carriers and patients. To prevent HBV intrauterine infection is very difficult for its mechanism not being known clearly. Our department have studied systematically in this field over ten years and have gotten some important results, which suggested that HBV intrauterine infection could be caused through hematogenous transfer and cellular transfer. This theory was mainly based on studies of term placentas. But much work must be done if we confirm it in first-trimester and second-trimester placentas. On the other hand, to study first-trimester and second-trimester placentas is necessary for clearly revealling the mechanisms and transplacental route and the early time of intrauterine infection. At present, there are only a few reports about aborted first-trimester placentas.[AIM] In this study, we will probe into (1)the status of HBV infection in aborted first-trimester placentas and second-trimester placentas and induced abortion fetal tissues; (2)the risk factors of first-trimester placentas infection; (3) the early time of intrauterine infection. This study might provide a theoretical basis for preventing intrauterine infection and exploring themechanism of HBV intrauterine infection.[METHODS} Aborted first-trimester placentas and venous blood from 25 HBsAg carrying pregnant women were collected. According to whether the placentas were infected or not, the HBsAg-positive pregnant women were divided into two groups: infection group and non-infection group. In this period, the sera and induced abortions tissues of 5 HBsAg carrying pregnant women were collected. Serologic HBV markers (HBsAg, anti-HBs, HBeAg, anti-Hbe, anti-HBc and HBV DNA) of pregnant women were determined by ELISA and PCR. The HBsAg, HBeAg and HBV DNA in placentas and fetal tissues were detected by SABC and in situ hybridization. HBV infected placental ultramicrostructure of the aborted first-trimester placentas were observed with transmission electron microscope. The epidemiological data were managed and analyzed by using the computer packages SPSS 10.0.[RESULTS ] 1. HBsAg positive rate in first-trimester pregnant women was 7%(25/355). The rate of HBsAg and HBeAg positive was 32%(8/25); and HBV DNA positive rate was 68%(17/25).2. HBsAg analog was detected in rough endoplasmic reticulum of trophoblastic cell, and the desmosomes were in good condition by transmission electron microscope.3. The first-trimester placentas HBV infection rate was 32%(8/25). Of the 25 first-trimester placentas, infection rate in decidual cell, trophoblastic cell, villous mesenchymal cell were 29.2%(7/24), 32%(8/25), 16%(4/25) respectively. HBsAg, HBeAg and HBV DNA were mainly located in the cytoplasm and karyon of infected cell.4. Case control study analysis showed that risk factors of HBV infecting first-trimester placentas were HBeAg positive in pregnant women (OR=12.5, P=0.008 ) and high concentration of maternal serum HBV DNA (OR=22.5,P=0.004). There were no correlation with other factors, such as history of HBsAg carrying, history of natural and/or artificial abortion and labour history.5. HBsAg, HBcAg and HBV DNA were detected not only in fetal liver, but also in fetal lung, fetal thymus, fetal heart and placenta. [CONCLUSION] (1)HBV may infect placentas of first-trimester pregnant. (2)Risk factors of HBV infecting first-trimester placentas were HBeAg positive in pregnant women and the high concentration of maternal serum HBV DNA.(3)Intrauterine infection HBV can express not only in fetal liver, but also in fetal lung, fetal thymus, fetal heart, placenta and fetal other tissues. (4)It is impossible for HBV to transfer the desmosomes being in good condition.It will become more difficult to make an effective approach to prevent HBV intrauterine transmission when the opinion about HBV infecting in first-trimester pregnant placentas is confirmed.
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