Table 1 . Pregnancy category of US Food and Drug Adminis tration-approved treatments for chronic hepatitis B virus.

Drugs	Pregnancy category
IFN-a	C
Peg-IFN-a	C
Adefovir	C
Entecavir	C
Lamivudine	C
Telbivudine	B
Tenofovir	B

Category A drugs: controlled studies in women fail to demonstrate a risk to the fetus.

Category B drugs: no teratogenic/embryogenic risk in animal studies and no controlled human studies available or risk in animal studies, but controlled human studies refute these.

Category C drugs: teratogenic/embryocidal effects in animals, and no controlled studies in humans.

Category D drugs: positive evidence of human fetal risk, but benefits from use in pregnant women may be acceptable despite the risk.