Abstract: ObjectiveTo investigate the changes and the development of hepatitis Bvirus serologic markers in mothers carry ing hepatitis Bsurface antigen(HBsAg)and theirinfants who accepted hepatitis Bimmunoglobulin(HBIG)combining hepatitis Bvaccine immunization by follow-up study.Methods125 HBsAg carrier mothers and their 128 infants(3 twin pairs)were followed up.Major HBVsero logic markers in all mothers and theirinfants were detected by enzyme-linked immunosorbent assay(ELISA)when infants were at month 7 and at month 24 to month 36.Results83 infants were followed up at month 7 and 75 infants and their mothers were fo llowed up when infants were at month 24 to month 36.Of 128 infants born to HBsAg-positive mothers,4 infants were HBsAg positive at birth,only 1 infant who was bor n from HBsAg-positive and HBeAg(hepatitis Be antigen)-positive mother was persistently positive sera for HBsAg.The other 94 infants were negative HBsAg.Of 26 infants born to HBsAg-positive and HBeAg-positive mothers,20 showed detectable levels of HBeAg.HBeAg were still detectable in 1 infant who was also HBsAg positive and the others all became HBeAg-negative during follow-up period.No infant became HBeAg-positive.Hepatitis Be antibody(anti-HBe)and hepatitis Bcore antibody(ant-i HBc)in the infants disappeared gradually in the shor-tterm and long-term follow-up.ConclusionThe transplacental intrauterine infection rate of HBVwas about 3.13% (4/128),and the chronic infection rate of HBV was about 25.00% (1/4).The maternal HBeAg may pass through placenta from mother to fetus,butit will disappearin 7 months in the infants.The sole existence of anti-HBe and(or)anti-HBc in infants simply represented the transplacental maternal antibo dies to the fetus,and may notindicate thatinfants experience HBVinfection actively or previously.