A 28-year-old woman in her third trimester of pregnancy tests positive for HBsAg. Further testing shows HBeAg positive, anti-HBe negative and serum HBV DNA of 8 × 10⁷ IU/mL. What is the risk of vertical transmission to the neonate without prophylaxis, and what prophylaxis strategy reduces this risk?
- A 70–90% risk in HBeAg-positive mothers; HBIG + hepatitis B vaccine at birth, plus antiviral therapy (tenofovir) in third trimester for high viral load ✓
- B 10–20% risk; hepatitis B vaccine alone given at birth
- C Less than 5% risk; anti-HBs antibody testing of neonate at 6 months suffices
- D 50% risk; HBIG alone within 12 hours is sufficient for prevention
Explanation
HBeAg-positive mothers with high viral load (>200,000 IU/mL) have 70–90% risk of vertical (perinatal) transmission without prophylaxis. Neonates should receive both HBIG (0.5 mL IM) AND hepatitis B vaccine within 12 hours of birth, followed by completion of the vaccine series. When maternal HBV DNA exceeds 200,000 IU/mL, current guidelines recommend adding tenofovir disoproxil fumarate from 28 weeks gestation to reduce viral load and further lower transmission risk. Vaccine alone is insufficient for high-viremia mothers. HBIG alone without vaccine is also suboptimal.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.