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

High viral load (HBV DNA >200,000 IU/mL):

• Initiate tenofovir disoproxil fumarate (TDF) at 24-28 weeks gestation 1
• Continue TDF until 12 weeks postpartum 1
• This significantly reduces intrauterine transmission risk 3

Low viral load (HBV DNA <200,000 IU/mL):

• Antiviral therapy is not required solely for prevention of perinatal transmission 1
• Monitor HBV DNA levels throughout pregnancy 1

Maternal Counseling and Education

HBsAg-positive women must receive comprehensive counseling covering 2:

• Modes of HBV transmission and prevention strategies
• Breastfeeding is safe and not contraindicated, even on antiviral therapy with tenofovir 1, 3
• Critical importance of immediate infant postexposure prophylaxis
• Hepatitis B vaccination for all household, sexual, and needle-sharing contacts
• Medical evaluation and possible treatment for chronic hepatitis B
• Substance abuse treatment referral if appropriate

Delivery Planning

• Delivery route should be based solely on obstetric indications, not HBV status 3
• Cesarean section does not reduce transmission risk when proper infant immunoprophylaxis is administered 4, 3
• Provide copy of HBsAg laboratory results to delivery hospital and newborn care provider 2
• Enroll in jurisdiction's Perinatal Hepatitis B Prevention Program (PHBPP) for case management 1

Critical Infant Management Protocol

Within 12 hours of birth (this timing is non-negotiable) 2, 1:

• Administer single-antigen hepatitis B vaccine
• Administer HBIG 0.5 mL at a different injection site

Special consideration for preterm infants (<2,000 g):

• The birth dose does NOT count toward the vaccine series due to reduced immunogenicity 2
• Administer 3 additional doses (total of 4 doses) starting at age 1 month 2

Complete vaccine series:

• Final dose must not be given before 24 weeks (164 days) of age 2

Postpartum Monitoring

Maternal monitoring:

• Monitor ALT and HBV DNA every 1-3 months for 6 months postpartum 1, 3
• Watch for hepatitis flare after delivery and after antiviral discontinuation 3

Infant follow-up:

• Perform postvaccination testing for anti-HBs and HBsAg at 9-18 months of age (typically at next well-child visit) 2
• Testing before 9 months may detect passively acquired maternal antibodies or HBIG, yielding false results 2
• Do NOT test for anti-HBc, as maternal antibodies persist up to 24 months 2

Special Procedural Considerations

• HBeAg-positive women or those with high HBV DNA should avoid invasive procedures like amniocentesis due to high transmission risk 1
• Prefer non-invasive prenatal testing over amniocentesis when possible 1

Common Pitfalls to Avoid

• Never delay infant immunoprophylaxis beyond 12 hours - this is the most critical intervention 2, 1
• Do not discourage breastfeeding; this outdated practice increases bottle feeding rates unnecessarily 4, 3
• Do not perform unnecessary cesarean sections for HBV prevention alone 4, 3
• Do not count the birth dose in preterm infants <2,000 g toward the vaccine series 2
• Ensure communication between transferring facilities about infant prophylaxis status 2