Hepatitis B Virus (HBV) can be transmitted from mother-to-child, with a risk increasing according to maternal HBV DNA viral load during the last trimester of pregnancy. Nucleosides analogues, lamivudine, telbivudine, or nucleotides analogues, tenofovir DF decrease HBV mother-to-child transmission risk, and are recommended in Guidelines (EASL 2012) for pregnant women with HBV DNA above 1,000 000 I.U/mL. HDV is a defective virus using HBs Ag for its own replication. HDV-HBV co-infection is a re-emerging infectious disease in western countries, due to immigration of people coming from endemic areas. Nucleosides analogues have only a minor impact on quantitative HBs Ag level (Boyd A et al. AIDS Research and Human Retroviruses 2013). Data about vertical HDV transmission are old (Rizzetto, et al. J Med Virol 1982), before a large use of nucleosides/nucleotides analogues in HBV infected pregnant women, justifying a new study.