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 require HBV DNA quantification to determine the need for antiviral prophylaxis, and their infants must receive both hepatitis B vaccine and HBIG within 12 hours of birth to prevent perinatal transmission. 1

Prenatal Testing and Initial Evaluation

• All pregnant women must be tested for HBsAg during the first trimester of each pregnancy, regardless of prior vaccination or testing history 2, 1
• Women not screened prenatally who engage in high-risk behaviors (injection drug use, multiple sex partners, STD treatment, HBsAg-positive partner) should be tested at hospital admission for delivery 2
• For newly diagnosed HBsAg-positive women, obtain HBV DNA quantification immediately to assess viral load and transmission risk 1

Antiviral Prophylaxis Decision Algorithm

The critical threshold is HBV DNA >200,000 IU/mL:

• If HBV DNA >200,000 IU/mL: Initiate tenofovir disoproxil fumarate (TDF) at 24-28 weeks gestation and continue until 12 weeks postpartum 1
• If HBV DNA <200,000 IU/mL: Antiviral therapy is not required solely for prevention of perinatal transmission, but monitor HBV DNA levels throughout pregnancy 1

This approach is based on evidence showing that high viral loads (>200,000 IU/mL) are associated with immunoprophylaxis failure despite appropriate infant vaccination and HBIG 3.

Maternal Counseling and Education

HBsAg-positive pregnant women must receive comprehensive counseling covering 2:

• Modes of HBV transmission and prevention strategies
• Perinatal safety: Breastfeeding is safe and not contraindicated, even on TDF 1
• Critical importance of infant postexposure prophylaxis within 12 hours of birth
• Hepatitis B vaccination for all household, sexual, and needle-sharing contacts 2
• Medical evaluation and possible treatment of chronic hepatitis B 2

Delivery Planning and Hospital Coordination

• Provide a copy of the HBsAg-positive laboratory report to the delivery hospital and the newborn's healthcare provider 2
• Refer to the jurisdiction's Perinatal Hepatitis B Prevention Program (PHBPP) for case management 1
• Delivery route should be based solely on obstetric indications, not HBV status 3
• Cesarean section does not reduce transmission risk when appropriate infant immunoprophylaxis is administered 3

Infant Immunoprophylaxis Protocol

This is the most critical intervention to prevent perinatal transmission:

For Term Infants (≥2,000 grams):

• Administer hepatitis B vaccine AND HBIG (0.5 mL) within 12 hours of birth at different injection sites 2, 1
• Complete the vaccine series according to the schedule for infants born to HBsAg-positive mothers 2
• Final dose must not be given before 24 weeks (164 days) of age 2

For Preterm Infants (<2,000 grams):

• Give hepatitis B vaccine and HBIG within 12 hours of birth 2
• The birth dose does NOT count toward the vaccine series due to reduced immunogenicity in preterm infants 2
• Administer 3 additional doses (total of 4 doses) beginning at 1 month of age 2

Critical Pitfall:

If the infant is transferred to another facility after birth, staff at both facilities must communicate regarding vaccination and HBIG status to ensure timely prophylaxis 2. This is a common point of failure in the prevention cascade.

Infant Follow-Up and Serologic Testing

• Perform postvaccination testing for anti-HBs and HBsAg at 9-18 months of age (typically at the next well-child visit) 2
• Do not test before 9 months to avoid detecting passively acquired anti-HBs from HBIG and to maximize detection of late HBV infection 2
• Do not test for anti-HBc, as maternal antibodies may persist until 24 months 2

Interpretation:

• Anti-HBs >10 mIU/mL and HBsAg-negative: Protected, no further management needed 2
• Anti-HBs <10 mIU/mL and HBsAg-negative: Consider revaccination 2

Maternal Postpartum Monitoring

• Monitor ALT and HBV DNA every 1-3 months for 6 months postpartum or after antiviral cessation 1, 3
• Beware of hepatitis flares after delivery and after stopping antivirals, which can occur in up to 30% of women 3
• Continue case management through PHBPP to ensure completion of infant vaccination series 1

Special Considerations

Invasive Prenatal Procedures:

• HBeAg-positive women or those with high HBV DNA should be counseled about increased transmission risk with amniocentesis 1
• Prefer non-invasive prenatal testing over amniocentesis when possible 1

Breastfeeding:

• Breastfeeding is NOT contraindicated for HBsAg-positive mothers, even when taking TDF 1, 3
• This is safe provided the infant receives appropriate immunoprophylaxis at birth 2

The evidence strongly supports that combined active-passive immunoprophylaxis (vaccine plus HBIG within 12 hours) is 85-95% effective at preventing perinatal transmission 4, 5. The addition of maternal antiviral therapy for high viral loads further reduces the 5-15% failure rate associated with intrauterine transmission 4, 3.