What is the recommended management for a pregnant woman who tests positive for hepatitis B surface antigen?

Management of HBsAg-Positive Pregnancy

All HBsAg-positive pregnant women with HBV DNA >200,000 IU/mL or who are HBeAg-positive should receive tenofovir disoproxil fumarate starting at 24–28 weeks gestation, and every infant born to an HBsAg-positive mother must receive both hepatitis B vaccine and HBIG within 12 hours of birth. 1, 2, 3

Screening and Initial Assessment

• Screen all pregnant women for HBsAg at the first prenatal visit, regardless of prior vaccination status or previous negative tests, because 30–40% of chronic HBV infections arise from perinatal transmission. 2, 3, 4

• Repeat HBsAg testing at hospital admission if maternal status is unknown or if new risk factors emerge (injection drug use, multiple sexual partners, recent STI). 2, 4

• Measure HBV DNA and ALT levels at 26–28 weeks gestation in every HBsAg-positive woman to determine candidacy for antiviral prophylaxis—this is the critical decision point. 1, 2, 3

• Test for HBeAg status because maternal HBeAg positivity correlates strongly with high viral load and transmission risk, and can serve as a surrogate marker when HBV DNA testing is unavailable. 5

Antiviral Therapy: When and What

• Initiate tenofovir disoproxil fumarate (TDF) at 24–28 weeks gestation when maternal HBV DNA exceeds 200,000 IU/mL (≈5.3 log₁₀ IU/mL) or when the mother is HBeAg-positive. 1, 2, 3 This timing allows adequate viral suppression before delivery while minimizing fetal drug exposure.

• TDF is the sole first-line agent for HBV treatment in pregnancy, with FDA safety data from ≥3,300 first-trimester exposures showing no increase in major birth defects compared to background rates. 2

• Continue TDF through 12 weeks postpartum for women who started prophylaxis during pregnancy to prevent postpartum hepatitis flares, which occur frequently after abrupt discontinuation. 2, 6

• Switch from entecavir to TDF before or during pregnancy because tenofovir has superior safety data in pregnancy (category B vs. category C). 2

• For women already on long-term HBV treatment (advanced fibrosis, cirrhosis, or active liver disease), continue TDF throughout pregnancy and postpartum—do not interrupt therapy. 1, 2

Earlier Treatment Considerations

• Women with evidence of significant liver disease (elevated ALT, advanced fibrosis on prior assessment) should continue or initiate antiviral therapy earlier in pregnancy, not just for transmission prevention but for maternal health. 1

• Starting antiviral therapy in the first or second trimester provides similar efficacy to third-trimester initiation and may be appropriate for women with active hepatitis. 1

Delivery Management

• Vaginal delivery is the preferred mode for all HBsAg-positive women; cesarean section should follow standard obstetric indications only. 1, 2 Elective cesarean solely for HBV prevention is not recommended by hepatology guideline bodies. 2

• The narrow exception: Consider cesarean section only for Asian, HBeAg-positive mothers with very high viral loads (>7 log₁₀ copies/mL or >6.14 log₁₀ IU/mL) who did not receive antiviral therapy. 2 This exception is based on a meta-analysis of 18 Chinese studies showing reduced transmission (pooled OR 0.42,95% CI 0.23–0.76). 2

• In practice, most high-viral-load women will receive TDF prophylaxis, eliminating the need for cesarean section in nearly all cases. 2

Prenatal Invasive Testing

• Prefer non-invasive prenatal testing (NIPT) over amniocentesis in HBeAg-positive or high-viral-load pregnancies because invasive procedures increase HBV transmission risk. 2

• Avoid chorionic villus sampling in women with high-risk HBV infection. 2

Neonatal Immunoprophylaxis (Critical)

• All infants born to HBsAg-positive mothers must receive both hepatitis B vaccine and HBIG within 12 hours of birth, regardless of whether maternal antiviral therapy was given. 1, 2, 3, 7 This dual prophylaxis reduces transmission from >90% to 5–10% in high-risk mothers. 2, 7

• Complete the vaccine series with doses at 1 month and 6 months of age; do not administer the final dose before 24 weeks of age. 3

• For infants weighing <2,000 g, do not count the birth dose toward the vaccine series due to reduced immunogenicity—administer 3 additional doses beginning at 1 month of age. 3

• Perform serologic testing for anti-HBs and HBsAg at 9–12 months (not before 9 months to avoid detecting passively acquired anti-HBs from HBIG). 2, 3 Infants with anti-HBs >10 mIU/mL and HBsAg-negative are protected and require no further management. 3

Breastfeeding

• Breastfeeding is safe and should be encouraged for all HBV-infected mothers, including those receiving TDF, because tenofovir levels in breast milk are low and do not increase infant risk. 1, 2, 3, 6

• Contraindications are limited to cracked or bleeding nipples in mothers with detectable HBV DNA and to infants with oral ulcers. 2

Postpartum Follow-Up

• Refer all HBsAg-positive mothers to the local Perinatal Hepatitis B Prevention Program for coordinated case management and counseling on household transmission prevention. 2, 3

• Monitor for hepatitis flares after delivery and after stopping antiviral therapy; check ALT every 1–3 months until 6 months postpartum. 2, 6

• Screen in every subsequent pregnancy, even if prior tests were negative or the mother was vaccinated, to avoid missed new infections. 2, 3

Common Pitfalls to Avoid

• Omitting third-trimester HBV DNA testing is the most common error—it fails to identify candidates for antiviral prophylaxis and leaves high-risk infants unprotected. 2

• Administering HBIG to the mother antenatally provides no benefit in preventing transmission; HBIG is effective only when given to the infant after birth. 2, 7

• Discouraging breastfeeding contradicts current evidence showing safety with proper infant immunoprophylaxis. 1, 2, 3

• Performing elective cesarean solely for HBV prevention offers no advantage when appropriate neonatal prophylaxis is administered and conflicts with guideline recommendations. 1, 2

• Using lamivudine for long-term therapy increases resistance risk; tenofovir is superior in efficacy and safety profile. 1, 2

• Continuing entecavir during pregnancy when tenofovir is the safer, evidence-based choice with more robust pregnancy safety data. 2