What are the management and prevention strategies for a pregnant woman who is Hepatitis B surface antigen (HBsAg) positive?

Management of HBsAg-Positive Pregnancy

All HBsAg-positive pregnant women should receive comprehensive prenatal testing, antiviral prophylaxis when HBV DNA exceeds 200,000 IU/mL, and their infants must receive both hepatitis B vaccine and HBIG within 12 hours of birth to prevent perinatal transmission. 1

Maternal Screening and Testing

• Test all pregnant women for HBsAg during the first trimester of every pregnancy, regardless of prior vaccination history or previous testing results 1
• Measure HBV DNA levels in all HBsAg-positive women to determine the need for antiviral therapy 1
• For women not screened prenatally who are at high risk, perform testing at hospital admission for delivery 1

Antiviral Prophylaxis During Pregnancy

Initiate maternal antiviral therapy when HBV DNA exceeds 200,000 IU/mL to prevent perinatal transmission 1. This threshold is critical because:

• Maternal HBeAg positivity correlates strongly with viral load and predicts transmission risk 2
• Women with HBV DNA >200,000 IU/mL have significantly higher rates of immunoprophylaxis failure in their infants 2
• Tenofovir is the preferred antiviral agent and is safe during pregnancy and breastfeeding 1, 3

Newborn Immunoprophylaxis Protocol

Within 12 hours of birth, administer both: 1, 4

• Hepatitis B immune globulin (HBIG): 0.5 mL intramuscularly 4
• Hepatitis B vaccine: First dose (10 μg for infants) 4

Critical timing considerations:

• HBIG efficacy decreases markedly if delayed beyond 48 hours 4
• The combination of HBIG plus vaccine is 85-95% effective in preventing chronic HBV carrier state 4, 5
• HBIG alone has only 50% efficacy, while the combination regimen is superior 4

Vaccine Series Completion

Complete the hepatitis B vaccine series as follows: 1

• Second dose at 1 month of age
• Third dose at 6 months of age
• Do not administer the final dose before 24 weeks of age 1

Special consideration for low birth weight infants (<2,000 g): 1

• Do not count the birth dose toward the vaccine series due to reduced immunogenicity
• Administer 3 additional vaccine doses beginning at 1 month of age (total of 4 doses)

Post-Vaccination Testing

Test all infants at 9-18 months of age for: 1

• Anti-HBs antibody levels
• HBsAg status

Do not test before 9 months to avoid detecting passively acquired anti-HBs from HBIG 1

Interpretation:

• Infants with anti-HBs >10 mIU/mL and HBsAg-negative are protected and require no further management 1
• Despite optimal prophylaxis, approximately 1.7% of infants may still experience immunoprophylaxis failure, particularly when maternal viral loads are very high 2

Breastfeeding Guidance

Breastfeeding is safe and should be encouraged when proper infant immunoprophylaxis is provided 1, 3. Key points:

• Breastfeeding does not increase HBV transmission risk when infants receive appropriate immunoprophylaxis 3, 5
• No need to delay breastfeeding initiation until after infant immunization 3
• Mothers on tenofovir therapy can safely breastfeed 1, 3
• Monitor and treat any breast conditions (cracked nipples) that could increase viral exposure 3

Delivery Considerations

Cesarean section is not recommended solely for the purpose of preventing HBV transmission 6. The evidence shows:

• Mode of delivery does not significantly impact transmission rates when proper immunoprophylaxis is given
• Despite high cesarean rates (82.3%) in some populations driven by HBV concerns, vaginal delivery with appropriate infant prophylaxis is equally safe 6

Case Management and Counseling

Refer all HBsAg-positive pregnant women to the Perinatal Hepatitis B Prevention Program for case management 1

Provide written documentation of maternal HBsAg status to: 1

• The delivery hospital
• The infant's healthcare provider

Counseling topics must include: 1

• Modes of HBV transmission and prevention strategies
• Importance of hepatitis B vaccination for household contacts, sexual partners, and needle-sharing contacts
• Safety of breastfeeding with proper infant immunoprophylaxis
• Need for infant follow-up testing at 9-18 months

Common Pitfalls to Avoid

• Do not delay HBIG administration beyond 12 hours after birth; efficacy drops significantly after 48 hours 4
• Do not count the birth vaccine dose in infants <2,000 g toward the series completion 1
• Do not test infants before 9 months of age, as this may detect passively transferred antibodies rather than active immunity 1
• Do not discourage breastfeeding based on maternal HBV status or antiviral therapy 1, 3
• Do not perform cesarean section solely for HBV prevention, as it provides no additional benefit when proper immunoprophylaxis is given 6