Vertical HIV transmission has been dramatically reduced by the use of combined antiretroviral therapy in HIV-infected pregnant women. Among the most often used drugs, several have dual activity, against HIV and HBV: lamivudine, emtricitabine, tenofovir. Studies about vertical HBV transmission from HIV-HBV co-infected pregnant women are rare in developed countries. The study hypothesis is a major reduction of the risk of HBV vertical transmission.