Untreated highly viraemic pregnant women from Asia or sub-Saharan Africa often transmit hepatitis B virus despite serovaccination to newborns

Background & Aims Mother‐to‐child (MTC) hepatitis B virus (HBV) transmission has been mainly studied in Asia. The geographical origins of women and HBV genotypes differ in Europe. The aims were to determine the rate and risk factors of MTC HBV transmission from women with high HBV DNA loads in a maternity hospital in Paris, France. Methods Retrospective study of HIV‐negative, HBs Ag‐positive pregnant women with HBV DNA loads above 5 Log10 I.U/ml who were not given lamivudine or tenofovirDF during pregnancy between 2004 and 2011. Results Among 11 417 pregnant women, 437 (4%) showed a positive HBs Ag. Among these women, 52 had HBV DNA loads above 5 Log10 I.U/ml: 41, 10 and 1 born in Asia, sub‐Saharan Africa and Europe respectively. Among the 52 women, 40 were eligible for the analysis: no antiviral therapy during pregnancy; children over 9 months old. Twenty‐eight (70%) women were assessed, corresponding to 41 childbirths. Eleven children (27%) had positive HBs Ag, 14 (34%) had positive HBc and HBs Ab, 16 (39%) had positive HBs Ab only. The risk of having positive HBs Ag, according to maternal HBV DNA loads, was 14% for HBV DNA loads less or equal to 8 Log10 I.U/ml, 42% for HBV DNA loads over 8 Log10 I.U/ml, P = 0.04, but not related to the women's origin, HBV genotype. Conclusions This study confirms that serovaccination does not fully protect newborns from MTC HBV transmission, when maternal HBV DNA loads exceed 5 Log10 I.U/ml, regardless of the women's origin or HBV genotype.