To analyze the mother-to-child transmission (MTCT) of hepatitis B virus (HBV) infection in pregnant and postpartum women, and explore the MTCT rate and its influencing factors in the real-world where strict preventive interventions measures are implemented.

A cohort study was conducted on 10 250 mothers of HBV-exposed children in Beijing from January 1st, 2021 to December 31st, 2023. Socioeconomic data, HBV serological markers, HBV viral load and MTCT prevention interventions were analyzed, respectively. The relationship between year, maternal age and positivity of hepatitis B virus surface antigen (HBsAg) were analyzed by Poisson regression analysis. Data of HBsAg-positive mothers and HBV-exposed children were sourced from the National Prevention of Mother-to-Child Transmission of HIV, Syphilis and Hepatitis B Information System. Post-vaccination serological testing (PVST) results and MTCT rates were described for 8 412 (82.07%) HBV-exposed children who completed follow-up serological testing after full vaccination. Mothers and children were grouped based on the HBV DNA load of infected mothers: pregnant women with high viral load group (1 780 cases) and pregnant women with low viral load group (8 470 cases), children with high-exposure group (1 664 cases) and children with low-exposure group (6 748 cases). The differences of basic information, fetal outcomes and prevention of MTCT interventions between two groups of pregnant women were analyzed by Chi-square test and Mann-Whitney test; the differences of MTCT rates under different socioeconomic, infection status and prevention of MTCT interventions were compared by Chi-square test.

From 2021 to 2023, there were a total of 403 368 deliveries in Beijing, including 10 093 HBsAg-positive delivery women (10 250 live born children were delivery women), the HBsAg positivity rate was 2.50% (95%CI: 2.45%-2.55%), with a downtrend that the younger of pregnant woman was, the lower the positive rate of HBsAg (RR = 0.93, P < 0.001). Timely vaccination rate of hepatitis B vaccine (99.94% vs. 99.76%) and timely injection rate of hepatitis B immunoglobulin (HBIG) (99.89% vs. 99.88%) of pregnant women in high viral load group and low viral load group were both higher than 99.50%, but without significant difference (χ² = 2.33, P = 0.127; χ² = 0.00,P = 0.950). The vaccination time of hepatitis B vaccine were 0.48 (0.26, 0.60) h and 0.53 (0.30, 1.15) h, respectively (Z = 12.83, P < 0.001); the injection time of HBIG in children with high exposure group and low exposure group were 0.41 (0.25, 0.51) h and 0.50 (0.28, 1.07) h, respectively (Z = 14.85, P < 0.001), both with significant differences. The antiviral treatment rate of pregnant women in high viral load group was 96.35% (1 715/1 780), significantly higher than that of the low viral load group (14.06%, 1 191/8 470) (χ² = 4 902.99, P < 0.001); the proportion of pregnant women in high viral load group delivered in specialized hospitals (89.94%, 1 601/1 780) was significantly higher than that of the low exposure group (34.90%, 2 956/8 470) (χ² = 1 805.80, P < 0.001), with significant difference. Total of 6 cases of MTCT were identified, the MTCT rate of HBV was 0.07% (95%CI: 0.02%-0.16%). Among different delivery ages, educational levels, types of delivery institutions and delivery methods, the MTCT rates of HBV were without significant difference (all P > 0.05). The MTCT rate of HBV in HBeAg positive pregnant women was higher than that of HBeAg negative pregnant women (0.28% vs. 0.00%: χ² = 17.15, P < 0.001), and the MTCT rate of HBV in high viral load pregnant women was higher than that of low viral load pregnant women (0.36% vs. 0.00%:χ² = 24.35, P < 0.001), both with significant differences.

Timely administration of HBIG and vaccination for all HBV-exposed children, combined with antiviral treatment starting in late pregnancy for mothers with high MTCT risk, could reduce the MTCT rate of HBV to an extremely low level.