Mother to child transmission(MTCT) is the main route of hepatitis B virus(HBV) transmission.High HBV DNA level of pregnant women is the main risk factor of MTCT. Many literatures demonstrate that using nucleoside (acid) analogs in late pregnancy can significantly reduce HBV DNA level and effectively blocking MTCT. Therefore, treatment guidelines of hepatitis B in Europe and the Asia Pacific region clearly pointed out: Nucleoside (acid) analogs can be used in pregnant women after 28 weeks of gestation for blocking MTCT in mothers with high HBV DNA level. At present, the drugs used in late pregnancy including lamivudine (LAM) ,telbivudine(LdT) and tenofovir(TDF).

The safety of nucleoside (acid) analogues used in late pregnancy on children is not clear.In most of the related researches,the observation termination was 7-12 months after birth, and most were concentrated on the blocking effect of MTCT.The long-term impact of Nucleoside (acid) analogues on children's development has not been reported in the literatures. The aim of this study is to make clear of the effect of nucleoside (acid) analogues used in late pregnancy on long-term impact of children's development.

The one year old children born in Beijing Ditan hospital and whose mothers had taken LAM,LdT or TDF during late pregnancy will be enrolled as study group, and eligible children whose mothers untreated will be enrolled as control group. The children's height, weight, nutritional status, developmental quotient and immune response to hepatitis B vaccine etc will be evaluated at baseline and at 3 years old. By comparing the children's development in different groups as well as in self-control of different ages, we will discuss the effect of Nucleoside (acid) analogues on children's long-term development.

Inclusion Criteria:

• The one year old children whose mothers had taken Lamivudine,Telbivudine or Tenofovir in late pregnancy(28-30 weeks of gestation);
• The one year old children whose mothers untreated in late pregnancy;
• Children had completed standard hepatitis B vaccine and hepatitis B immune globulin combined active and passive prophylaxis;
• HBV DNA level of the children's mothers were over 6.0 log10 IU/ml before 28 weeks of gestation.

Exclusion Criteria:

• Children whose mothers over 35 years old at delivery;
• The couple having family hereditary disease or abnormal malformation has been found at fetal screening before 28 weeks gestation;
• History of amniocentesis during pregnancy;
• Co-infection with either hepatitis C virus, hepatitis D virus, human immunodeficiency virus, syphilis, toxoplasmosis, rubella or cytomegalovirus.
• Complications of pregnancy-induced hypertension, premature rupture of membranes, preterm birth, placenta previa or placental abruption; asphyxia at birth.

The one year old children born in BeiJing DiTan Hospital and whose mothers had taken Lamivudine, Telbivudine or Tenofovir and untreated in late pregnancy with HBV DNA level over 6.0 log10 IU/ml