There is insufficient evidence on the effects of entecavir in pregnant women, and there are no clear findings on the potential teratogenic risk to the fetus, so it is not advisable to have children while taking entecavir. Entecavir is a guanine nucleoside analogue that inhibits the hepatitis B virus polymutase by phosphorylating it into an active triphosphate, which competes with the natural substrate of hepatitis B virus polymutase, deoxyuridine triphosphate, to inhibit the activity of the virus. Entecavir is mainly used for the treatment of hepatitis B, etc. Because the effects on women during pregnancy are not well studied, nor are the potential risks to the fetus, and theoretically has some embryotoxicity, entecavir should not be taken during pregnancy preparation. If you are taking entecavir you must choose instrumental contraception and not get pregnant, and you must wait until three months after entecavir is discontinued before you consider preparing for pregnancy because of the potential embryotoxic and teratogenic effects.