The four nucleoside antiviral drugs currently on the market are lamivudine, entecavir, adefovir and telbivudine; the first three drugs belong to pregnancy category C drugs and only telbivudine belongs to category B. Pregnancy category C drugs were found to have certain mutagenic effects and may induce chromosomal aberrations when genotoxicity studies were conducted; and certain embryotoxic and embryonic malformation effects when used in high doses when reproductive toxicity studies were conducted. The risk of nucleoside antivirals to the developing human embryo is unclear, so women of childbearing age using nucleoside analogs should use effective contraception. Due to the potential presence of drug components in breast milk, it is best for nursing women not to use these drugs. If a pregnant woman with hepatitis B has a sudden attack of hepatitis and active viral replication during pregnancy, she can use nucleoside antiviral drugs along with hepatoprotection; the preferred drugs are tebivudine or lamivudine.