Abstract: Objective The aim of this study was to compare efficacy and safety of tenofovir alafenamide fumarate (TAF) and tenofovir disoproxil fumarate (TDF) in terminating mother to child transmission (MTCT) of hepatitis B viral infection. Methods 112 pregnant hepatitis B virus carriers with serum HBeAg positive were encountered in Beijing You'an Hospital, Capital Medical University between July 2021 and August 2022, and all received TAF (n=57) or TDF (n=55) antiviral therapy for blocking viral transmission, which discontinued before giving birth. All infants received standardized immune inoculation and were evaluated for serum HBV markers and HBV DNA loads at seven to nine month ages. Results Before delivery, incidence rates of premature birth, intrahepatic cholestasis of pregnancy, hypertensive disorder complicating pregnancy, premature rupture of membranes, slightly less amniotic fluid and oligohydramnios in the TAF-treated group were 7.0%, 8.8%, 7.0%, 12.3%, 7.0% and 3.5%, all not much different compared to 5.5%, 9.1%, 5.5%, 10.9%, 3.6% and 0.0% in TDF-treated group (all P>0.05); serum ALP level in TAF group was (146.1±44.3)U/L, much lower than [(166.9±52.5)U/L, P＜0.05] in TDF group; urine protein positive rate in TAF group was 7.0%, much lower than 23.6%(P＜0.05) in TDF group; there were no significant differences as respect to serum ALT, AST, bilirubin, serum creatinine, phosphorus, calcium and glomerular filtration rates in the two groups (P>0.05); serum HBV DNA load in the TAF group was (3.4±0.7)lg IU/ml, much higher than [(2.9±0.8)lg IU/ml, P＜0.05] in TDF group; no MTCT occurred in the two group. Conclusion Antiviral therapy with TAF during pregnancy could efficaciously block MTCT of HBV infection in pregnant women with chronic HBV carriers, with higher renal safety.

Key words: Hepatitis B viral carriers, Tenofovir alafenamide fumarate, Pregnancy, Fetus, Renal toxicity, Maternal to child transmission