['Hepatitis B virus (HBV) intrauterine transmission from infected mothers contributes significantly to the persistence of the high number of HBV carriers. The aim of this study was to identify potential risk factors for HBV intrauterine transmission.', "A case-control study was performed on pregnant women tested positive for HBsAg at Shaanxi Maternal and Neonatal Health Hospital, Xi'an, China, from September 2002 to October 2004. Serum samples were taken from infected women and their newborn infants and used for the detection of HBsAg. A structured standard questionnaire was used to collect demographic, medical and maternal data, and maternal HBV DNA, HBeAg, anti-hepatitis C virus and anti-hepatitis D virus were also assessed. Ten neonates validated as having HBV intrauterine transmission were selected as cases and others as controls.", 'The univariate analysis indicated that maternal HBeAg positivity (odds ratio [OR] = 5.96, 95% confidence interval [CI]: 1.61-22.12), HBV DNA positivity (OR = 12.09, 95% CI: 2.97-40.17) and sexual intercourse in the second trimester (OR = 9.15, 95% CI: 1.08-202.99) were significantly associated with an increased risk for HBV intrauterine transmission, whereas contraceptive measures before pregnancy (OR = 0.21, 95%CI: 0.04-0.99) were associated with a decreased risk. The multivariate analysis, however, identified maternal HBV DNA positivity (OR = 19.18, 95%: CI: 3.26-118.73) and sexual intercourse in the second trimester (OR = 1.29, 95%: CI: 1.00-1.66) as the only independent risk factors for HBV intrauterine transmission.'] Are maternal hepatitis B virus ( HBV ) DNA positivity and sexual intercourse associated with HBV intrauterine transmission in China : a prospective case-control study?