Can a pregnant woman safely receive the hepatitis B vaccine?

Hepatitis B Vaccination in Pregnancy

Yes, pregnant women can and should receive the hepatitis B vaccine if they are at risk for HBV infection—the vaccine is safe throughout all trimesters and does not increase adverse pregnancy outcomes. 1, 2, 3

Who Should Receive Hepatitis B Vaccine During Pregnancy

Pregnant women meeting any of the following high-risk criteria should be offered vaccination: 4, 1, 2

• More than one sex partner in the previous 6 months 4, 2
• Evaluation or treatment for a sexually transmitted infection 4, 2
• Recent or current injection-drug use 4, 2
• HBsAg-positive sex partner 4, 2
• Household contact with a chronically infected person 1

Any pregnant patient who requests the vaccine can be offered vaccination, regardless of documented risk factors. 2, 3

Safety Profile

The hepatitis B vaccine has an excellent safety record in pregnancy across multiple large studies:

• The vaccine contains non-infectious hepatitis B surface antigen particles that pose no theoretical or documented risk to the fetus. 1
• A Vaccine Safety Datalink study of over 650,000 pregnancies found no increased risk of gestational hypertension, gestational diabetes, pre-eclampsia, cesarean delivery, preterm delivery, low birthweight, or small for gestational age infants among women who received HepB during pregnancy. 5
• Multiple studies demonstrate no increased risk of abortion, stillbirth, congenital malformations, or sudden infant death syndrome following vaccination during pregnancy. 1, 6
• The most common adverse event is injection site discomfort (10.5%), with no serious adverse events reported. 7

Vaccination Schedule and Administration

The standard three-dose series (0,1, and 6 months) should be initiated and can be completed during pregnancy. 1, 3

An accelerated schedule of 0,1, and 4 months is effective and practical for pregnant women, achieving 90% seroconversion rates after three doses. 7

• After one dose: 56% seroconversion 7
• After two doses: 77% seroconversion 7
• After three doses: 90% seroconversion 7

The vaccine must be administered intramuscularly in the deltoid muscle—never in the buttock, as this markedly reduces immunogenicity. 1

If a scheduled dose is missed, administer it as soon as possible without restarting the series. 1

Critical Distinction: Maternal vs. Neonatal Protection

The vaccine protects the mother from acquiring HBV infection during pregnancy but does NOT prevent infant infection if the mother is already HBsAg-positive. 2, 3

Infants born to HBsAg-positive mothers require both hepatitis B immune globulin (HBIG) and vaccine within 12 hours of birth for protection. 4, 2, 3

Universal Screening Requirement

All pregnant women must be tested for HBsAg during the first trimester of every pregnancy, even if previously vaccinated or tested. 4, 2, 3

Women at high risk who test negative initially should be retested late in pregnancy. 4

This screening identifies chronically infected women who need antiviral therapy consideration and ensures infants receive timely prophylaxis. 2

Post-Exposure Prophylaxis

Pregnant women exposed to HBV (e.g., sexual contact with acute hepatitis B) should receive both HBIG and begin the vaccine series within 14 days, using the same protocol as non-pregnant individuals. 1

Combined HBIG plus vaccine is more effective than vaccine alone for preventing infection after exposure. 1

Breastfeeding

Hepatitis B vaccination is not contraindicated during breastfeeding and can be administered safely while lactating. 1

Infants of HBsAg-positive mothers may be breastfed immediately after birth. 4

Common Pitfalls to Avoid

• Do not postpone vaccination in pregnant women at risk due to unfounded safety concerns—the vaccine is explicitly safe during pregnancy. 1, 2, 3
• Do not administer the vaccine in the buttock, as this significantly lowers immunogenicity in adults. 1
• Do not restart the vaccination series if a dose is missed; simply administer the missed dose promptly. 1
• Do not assume vaccination protects the infant from vertical transmission if the mother is already infected—these infants still require HBIG and vaccine at birth. 2, 3
• Do not skip universal HBsAg screening in any pregnancy, even if the woman was previously vaccinated. 4, 2, 3

Factors Affecting Response

Body mass index is inversely associated with seroconversion rates, though there is no single BMI threshold above which seroconversion fails to occur. 7