Abstract： Objective To explore the risk factors of and the influence of different hepatitis B virus (HBV) DNA load on paternal vertical transmission of HBV.Methods Totally,161 HBsAg negative women,whose husband was HBsAg positive,attended the antenatal clinics of the Provincial Maternity and Child Health Hospital of Fujian from September 2007 to December 2008 and their newborns were selected,and the epidemiologic information,the duration of being a HBV carrier,the first class HBV family history of the fathers,HBV markers,HBV DNA load,HBsAb of the gravidas,the outcomes of the newborns were all collected.Cord blood was sampled after delivery for HBV DNA quantification and those with HBV DNA load ≥1.0×103 copy/ml were chosen as the case group and those ＜ 1.0×103 copy/ml as control.Results (1) Among the 161 newborns,36 HBV DNA positive cord blood samples were detected,giving a rate of 22.4% (36/161) for paternal vertical transmission of HBV.The HBV DNA positive rate in cord blood was 32.0% (23/72) in HBeAg-positive fathers and 14.6% (13/89) in HBeAg-negative fathers.(2) Univariate analysis showed that HBeAg-positive,HBV DNA positive,first class family history of HBV and the duration of being a HBV carrier of the fathers were risk factors of paternal HBV vertical transmission[X2= 6.892,29.916,29.499 and 23.821,OR = 2.7,5.2,8.3 and 1.4 (P＜0.01)].(3) Multivariate analysis found that paternal serum HBV DNA positive and the first class family history of HBV of the father side were risk factors of paternal vertical transmission of HBV (OR = 11.1,95% CI;4.6-27.1;OR = 17.1,95% CI:3.5-82.6).(4) According to the different serum HBV DNA load of the HBsAg-positive father,7 groups were divided.A dose dependent effect was found that the HBV DNA positive rate of the cord blood increased with the rising of HBV DNA load.No HBV DNA positive cord blood was detected when paternal HBV DNA load was＜1.0×104 copy/ml,while 100% of the cord blood were positive when paternal HBV DNA load≥1.0×108 copy/ml.(5) The average birth weight of the newborns in the two groups was the same (3.3±0.4) kg.And the delivery mode,gestational age at delivery,height and Apgar score of the newborns at 1 minute,neonatal pathological jaundice and other complications had no significant difference between the two groups (P ＞ 0.05).No relationship was found between the neonatal outcomes and the paternal HBV vertical transmission (P＞0.05).Conclusions HBV DNA load in the serum of HBsAg-positive father,and the paternal first class family history of HBV are risk factors of paternal HBV vertical transmission.When the serum HBV DNA load in HBsAg-positive father is≥1.0×107 copy/ml,the possibility of paternal vertical transmission of HBV would increase.