Hepatitis B virus mother-to-child transmission among HIV-infected women receiving lamivudine-containing antiretroviral regimens during pregnancy and breastfeeding.

The study included 309 HIV-infected pregnant women receiving a lamivudine-containing antiretroviral regimen from week 25 of gestational age until 6 months postpartum, during breastfeeding. Twenty-seven of them (8.7%) were hepatitis B virus surface antigen (HBsAg) positive; at baseline, hepatitis B virus (HBV) DNA levels >3 log(10) IU/mL (with a median level of 6.2 log(10) IU/mL) were found in 10 women, who at one, three and six months postpartum had median levels of 5.2 log(10) IU/mL, 4.5 log(10) IU/mL and 2.8 log(10) IU/mL, respectively. Twenty-four of the 30 breast milk samples evaluated had undetectable HBV DNA and the other six had values between 15 and 155 IU/mL. Median lamivudine concentrations were 1070 ng/mL in serum and 684 ng/mL in breast milk. Among the 24 HBV-exposed children with available samples, 16 always tested negative, four had a transient infection, one had an undetermined status and three (12.5%) first tested positive at Month 12 or Month 24. Among the children born to the HBV-uninfected mothers of the same cohort, the rate of HBsAg positivity at 12-24 months was 2% (4/196). Our finding of the absence of significative levels of HBV DNA in the breast milk of co-infected mothers supports the present recommendations for breastfeeding in HBV-infected women. Horizontal transmission can be hypothesized for the infections detected in children at 12-24 months. Children born to HBV-positive mothers remained at higher risk of postnatal HBV acquisition compared to those born to HBV-negative women.