目的：探讨乙型肝炎病毒(HBV)母婴传播的影响因素，寻求降低婴儿HBV感染率的方法。方法：HBV携带及慢性乙型肝炎孕妇共635例，分别比较不同血HBV DNA滴度，不同分娩方式（剖宫产或自然分娩），以及不同肝功能状态孕妇所生婴儿出生时及3月龄时HBV的感染率。新生儿生后12 h内肌注乙肝免疫球蛋白200 U 及重组酵母乙肝疫苗10 μg；生后即刻显示血清HBV感染存在者，14 d时再肌注乙肝免疫球蛋白200 U。结果：孕妇高滴度组（HBV DNA>105拷贝/mL）所生新生儿出生时（14.4% vs 4.1%，P<0.01）与3月龄时（4.7% vs 0,P<0.01）HBV感染率均高于低滴度组（HBV DNA ≤105拷贝/mL）。两组新生儿3月龄时HBV感染率均低于出生时（P<0.05）。自然分娩的孕妇其婴儿出生时HBV感染率明显高于剖宫产组（P<0.01），但3月龄时，两组感染率接近。HBV携带孕妇所生婴儿出生时HBV感染率明显高于慢性乙型肝炎孕妇所生婴儿（P<0.01），但3月龄时两组婴儿HBV感染率亦接近。结论：孕妇血清HBV DNA水平与新生儿HBV宫内感染密切相关，故降低孕妇血清HBV DNA水平可能成为减少新生儿HBV感染的一种有效途径。在乙肝免疫球蛋白及重组酵母乙肝疫苗的双重保护下，孕妇的分娩方式与肝功能状态对HBV母婴传播无影响。

OBJECTIVE: To study the factors influencing mother-infant vertical transmission of hepatitis B virus (HBV). METHODS: A total of 635 pregnant women with chronic hepatitis B or chronic asymptomatic HBV carriers were enrolled. The rate of HBV infection was compared between the infants born from the pregnant women of different HBV-DNA load, different ways of delivery and different liver functions at birth and 3 months after birth. The newborn infants were routinely injected with hepatitis B immunoglobulin (200 IU) and hepatitis B vaccine (10 μg) within 12 hrs of birth. The newborns presenting HBV infection within 24 hrs of birth by serum test were re-injected with hepatitis B immunoglobulin (200 IU) 14 days after birth. RESULTS: The rate of HBV infection in infants with maternal HBV-DNA load >105 copies/mL was higher than in those with maternal HBV-DNA load ≤105copies/mL at birth (14.4% vs 4.1%; P<0.01) and 3 months after birth (4.7% vs 0; P<0.01).The rate of HBV infection at 3 months was lower than at birth in both groups. The rate of HBV infection in infants born by natural labor was higher than in those born by caesarean birth at birth (P<0.05), however, by 3 months after birth, the rate of HBV infection between the two groups was similar. The rate of HBV infection was higher in infants born to chronic asymptomatic HBV carrier mothers than that in infants born to chronic hepatitis B mothers at birth (P<0.01), but there were no significant differences in the two groups 3 months later. CONCLUSIONS: The maternal HBV-DNA load is correlated with the rate of HBV infection of infants. It might thus be an effective way to reduce the rate of HBV infection in infants by decreasing maternal HBV-DNA load. With the administration of hepatitis B immunoglobulin and hepatitis B vaccine, the delivery way and the liver function of pregnant women may not to be factors influencing mother-infant HBV vertical transmission.