Specimens applied for evaluating intrauterine infection include amniotic fluids, placental tissue and neonatal peripheral blood. Because postnatal sample is inevitably to be contaminated by maternal blood during delivery, it would be useless to determine the time when the infection was occurred (before or during the partum). A better alternative is detecting fetal infection before the partum by prenatal diagnostic technique. Comparing to the postnatal specimens, intrauterine specimens obtained from amniocentesis or cordocentesis can minimize the contamination of maternal blood. It is also a safety technique and the risk of nosocomial infection caused by invasive procedures is very low. The aim of this study was to investigate the fetal hepatitis B seroepidemiology by prenatal diagnostic technique and to find the evidence of HBV vertical transmission via spermatozoa.