Abstract: Objective The aim of this study was to investigate blocking hepatitis B virus (HBV) maternal-infant transmission by tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide fumarate (TAF) in hepatitis B viral carriers. Methods 99 pregnant women carrying HBV were enrolled in our hospital between January 2022 and January 2025, and were assigned to receive TAF (n=45) or receive TDF (n=44) at 28 weeks of gestation until delivery completed. 99 neonates were vaccinated with hepatitis B vaccine and hepatitis B immunoglobulin immediately after birth, and were followed-up for 12 months after delivery. Serum biochemical parameters and urinary β2-microglobulin (β2-MG) levels were detected routinely, and estimated glomerular filtration rate (eGFR) was calculated. Serum HBsAg level was detected by ELISA, and serum HBV DNA loads were detected by real-time fluorescence quantitative PCR. Multivariate binary Logistic regression analysis was applied to analyze the factors affecting blocking efficacy. Results By delivery, there were no significant differences as respect to serum ALT levels, HBV DNA loads and eGFR between the two groups (P>0.05), while urine β2-MG level in TDF group was (2.0±0.4)mg/L, much higher than [(0.4±0.1)mg/L, P<0.05] in TAF group; incidences of adverse outcomes related to pregnancy both in women or infants (13.3% vs. 15.9%) in the two groups were not significantly different (P>0.05); successful blocking in the two groups (95.6% vs. 93.2%) was also not significantly different (P>0.05); ages of pregnant women, baseline serum HBV DNA loads and percentage of formula feeding in 5 children with failed blocking were much older, greater or higher (P<0.05), while body mass of newborns at delivery was much lower than in 94 children with successful blocking(P<0.05); multivariate Logistic regression analysis showed that older pregnant women, higher baseline serum HBV DNA loads and lower body mass at birth were all the impacting factors for failed blocking(P<0.05). Conclusion Both TDF and TAF have a similar antiviral efficacy for blocking mother-to-child HBV transmission in pregnant women carrying HBV, and whether antiviral intervention should be started in advance needs clinical investigation.

Key words: Hepatitis B virus carriers, Pregnant women, Tenofovir disoproxil fumarate, Tenofovir alafenamide fumarate, Maternal-infant transmission, Blocking