Mother-to-Child HIV transmission has been dramatically reduced by the use of combined antiretroviral therapy in HIV-infected pregnant women, both in developed and in developing countries. Among the most often used drugs, several have dual activity, against HIV and HBV: lamivudine, emtricitabine, tenofovir; they can be used as a combo, as tenofovir+emtricitabine for instance. 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 in this context, justifying this retrospective study.