How should a 6‑week pregnant woman who is not immune to hepatitis B be managed?

Management of a 6-Week Pregnant Woman Not Immune to Hepatitis B

A pregnant woman at 6 weeks gestation who lacks hepatitis B immunity should receive the hepatitis B vaccine series immediately, as vaccination is safe during pregnancy and will protect both her and her infant from this potentially life-threatening infection. 1

Immediate Actions

Confirm Serologic Status

• Verify that the patient is truly non-immune by checking for absence of hepatitis B surface antibody (anti-HBs), and simultaneously confirm she is not currently infected by testing for hepatitis B surface antigen (HBsAg). 2
• If HBsAg testing was not performed during initial prenatal screening, order it immediately—universal first-trimester HBsAg screening is mandatory for all pregnant individuals regardless of vaccination history. 2

Initiate Hepatitis B Vaccination Series

• Start the 3-dose hepatitis B vaccine series now (at 6 weeks gestation) using the standard schedule: dose 1 today, dose 2 at 1 month, and dose 3 at 6 months. 1
• Hepatitis B vaccination during pregnancy carries no teratogenic risk and is explicitly recommended by the Advisory Committee on Immunization Practices (ACIP) for pregnant women at risk of HBV infection. 1

Risk Assessment and Counseling

Identify High-Risk Exposures

• Assess for ongoing HBV exposure risks including: multiple sex partners in the past 6 months, history of sexually transmitted infections, current or recent injection drug use, or an HBsAg-positive sexual partner. 1
• If any high-risk factors are present, counsel on additional prevention methods (barrier contraception, avoiding needle sharing) while awaiting vaccine-induced immunity. 1

Explain the Timeline of Protection

• Inform the patient that protective antibody levels typically develop 1–2 months after the third vaccine dose, so she will not be fully protected until late second or early third trimester. 3
• Emphasize strict avoidance of high-risk exposures during the first and second trimesters when she remains vulnerable. 1

Monitoring Through Pregnancy

Repeat HBsAg Testing at Delivery

• Even if the patient was HBsAg-negative in the first trimester, repeat HBsAg testing at hospital admission for delivery to detect any acute infection acquired during pregnancy. 1
• This repeat testing is critical because 30–40% of chronic HBV infections arise from perinatal transmission, and maternal infection status directly determines neonatal management. 2

Post-Vaccination Serologic Testing (Optional but Recommended)

• Consider checking anti-HBs levels 1–2 months after the third vaccine dose to confirm seroconversion, especially if the patient has chronic liver disease or immunocompromising conditions that reduce vaccine response rates. 4
• If anti-HBs is <10 mIU/mL after the complete series, administer a second 3-dose series postpartum. 4

Neonatal Planning

If Mother Remains HBsAg-Negative at Delivery

• The infant should receive the first dose of hepatitis B vaccine within 24 hours of birth (standard newborn protocol), then complete the series at 1–2 months and 6–18 months of age. 1
• No hepatitis B immune globulin (HBIG) is needed for the infant. 1

If Mother Tests HBsAg-Positive at Delivery (Acute Infection During Pregnancy)

• The infant must receive both hepatitis B vaccine and HBIG (0.5 mL) within 12 hours of birth at separate injection sites. 1, 2, 5
• Complete the infant vaccine series at 1 month, 2 months, and 6 months, then test for HBsAg and anti-HBs at 9–12 months to confirm protection. 1, 5
• Dual prophylaxis reduces mother-to-child transmission from >90% to 5–10%. 2

Common Pitfalls to Avoid

• Do not delay vaccination until after the first trimester—there is no safety concern, and earlier vaccination provides earlier protection. 1
• Do not assume prior vaccination equals immunity—up to 16% of individuals vaccinated as infants lose detectable antibody by adulthood, though immunologic memory usually persists. 3
• Do not omit repeat HBsAg testing at delivery—acute maternal infection during pregnancy will be missed if only first-trimester screening is performed. 1, 2
• Do not administer HBIG to the mother—antenatal maternal HBIG is ineffective at reducing transmission and should never be given. 2