Tenofovir disoproxil and telbivudine are categorized as
class B regarding safety in pregnancy and the other HBV drugs as
class C. Lamivudine and tenofovir disoproxil have not been shown to be associated with fetal abnormalities even when used during the first trimester of pregnancy.[73] (extracted from an article in Nature by Prof. Anna Lok]
3. So, I think Lamivudine is safe. You must consult your doctors, including your Obstetrician, they must work as a team to look after you and your baby.