ABSTRACT
<p><b>OBJECTIVE</b>Case-control study was employed to explore the association of sexual behavior during pregnancy and hepatitis B virus (HBV) intrauterine infection.</p><p><b>METHODS</b>212 HBsAg positive pregnant women were consecutively collected and investigated as objects. Those neonates detected for HBsAg with S/N value > or = 5 by Abbott reagents in periphery sera were selected as cases, others as controls. Information on sexual behavior during pregnancy, maternal HBeAg status and other factors was collected, and were analyzed with univariate analysis, multivariate logistic regression analysis, etc, to explore the association of factors with HBV intrauterine infection.</p><p><b>RESULTS</b>Ten of the 214 neonates were validated as occurrence of HBV intrauterine infection. Sexual behavior in the second trimester during pregnancy, with odd ratios 9.15 (95% CI: 1.10 - 76.28), as well as maternal positivity for HBeAg and HBV DNA, was significantly associated with HBV intrauterine infection, and sequently affirmed by multiple logistic regression analysis. The strength of association increased with frequency of sexual behavior. Interaction analysis suggested that there was synergistic interaction between maternal positivity of HBeAg and sexual behavior in the second trimester.</p><p><b>CONCLUSION</b>Sexual behavior was a newly discovered risk factor for HBV intrauterine infection, which need to be estimated in future studies. Inhibition of virus replication and moderate control of sexual behavior would be helpful to prevent HBV intrauterine infection.</p>