Pregnancy only mildly affects that natural progression of acute and chronic infection by the hepatitis B virus (HBV) but it does bring to light three important questions. Mother to child (vertical) transmission risk is best prevented by mandatory HBs antigen testing in all pregnant women in their second trimester and by systemic serovaccination of newborns of infected mothers. In mothers with high viral load, vertical infection in utero could be prevented by lamivudine, telbivudine or tenofovir treatment. Invasive obstetric or gynecological procedures (such as amniocentesis, forceps, etc.) do not seem to increase the risk of vertical infection. Breastfeeding is not contraindicated in maternal HBV infection after serovaccination of the newborn. This holds true for mothers on active treatment with tenofovir which is not absorbed into breast milk. When it comes to managing active antiviral treatment, in absence of virosuppression with lamivudine, tenofovir remains a logical step-up treatment; in absence of virosuppression with adefovir, tenofovir also remains a logical step-up choice as do tenofovir/emtricitabine combinations or lamivudine in absence of preexisting resistance which may have been induced during combination treatment of adefovir and lamivudine. In cases of effective virosuppression with treatment by analogues, lamivudine should be continued and entecavir should eventually be replaced by lamivudine, telbivudine or tenofovir; adefovir should be replaced by tenofovir or lamivudine in absence of resistance (which would require tenofovir therapy) or adefovir which would restrict lamivudine therapy.Le texte complet de cet article est disponible en PDF.