The 12 pregnant women enrolled willing to receive injections of HBIG (200 IU, S20023028, Hualan Biological Engineering Inc.) beginning at week 20 of gestation (at weeks 20, 24, 28, 32, 34, 36, 38, 39, and 40). The control group only underwent regular examinations without any HBIG treatment during pregnancy. All the infants born received combined immunoprophylaxis (HBIG, 200 IU, and the first dose of the hepatitis B vaccine, 5 μg, S19983018, Shenzhen Kangtai Biological Products Co. Ltd.) at different injection sites within 12 h postpartum.