SUPERStudy: Hepatitis B Transmission in Pregnancy

By usmlevideoss

Introduction: Hepatitis B virus (HBV) is a significant global health concern and can be transmitted from mother to child during pregnancy or delivery. Perinatal transmission is the most common mode of HBV acquisition in high-prevalence regions and poses a risk of chronic HBV infection in the newborn.

Hepatitis B is typically transmitted by inoculation of infected blood or blood products or through sexual intercourse. The virus is contained in most body secretions, and infection by parenteral and sexual contact has been documented. Groups at risk for hepatitis B infection are intravenous drug users, men who have sex with men, health care personnel, spouses of hepatitis carriers, those with multiple sexual partners, and Southeast Asian emigrants.

Approximately 5–10% of people infected with hepatitis B virus become chronic carriers of the virus. The incubation period is 6 weeks to 6 months. 

In the absence of prophylaxis, the risk of vertical transmission to the fetus is as high as 90% and is higher in the mothers who are HBeAg-positive or who have high serum HBV DNA levels. 

Modes of Transmission in Pregnancy

1.Vertical Transmission (Mother-to-Child):

  • In Utero (Rare): Occurs through transplacental transmission if there is placental leakage or viremia.
  • Peripartum (Most Common): Exposure to maternal blood or vaginal secretions during delivery.

2.Postpartum: Through breastfeeding, although the risk is negligible if the newborn receives appropriate prophylaxis.

Risk Factors for Transmission

  • Maternal HBV DNA Levels: High maternal viral load (>200,000 IU/mL) significantly increases the risk of transmission.
  • HBeAg Status: Hepatitis B e-antigen positivity correlates with higher infectivity and risk of perinatal transmission.
  • Mode of Delivery: Vaginal delivery and cesarean section have similar risks when prophylaxis is administered.
  • Inadequate Neonatal Prophylaxis: Lack of timely hepatitis B immunoglobulin (HBIG) and HBV vaccine increases the risk.

Screening and Diagnosis

1.Maternal Screening: All pregnant women should be screened for hepatitis B surface antigen (HBsAg) during the first trimester. Additional testing for HBeAg, HBV DNA levels, and liver function tests if HBsAg-positive. Transmission of the virus to the baby is likely if both surface antigen and e antigen are positive.

2.Neonatal Testing: Infants born to HBsAg-positive mothers should be tested for HBsAg and anti-HBs (hepatitis B surface antibody) at 9–12 months of age to confirm immunity and exclude infection.

Prevention of Vertical Transmission

1.Maternal Management:

•Antiviral Therapy: Tenofovir disoproxil fumarate (TDF) is the preferred choice for antiviral treatment in pregnancy. It is safe during pregnancy. Treatment should be

considered when maternal HBV DNA is greater than 200,000 IU/mL and started at week 28–32 of pregnancy to allow adequate time for viral suppression. Antiviral therapy need not be continued postpartum. 

  • Monitoring: Regular liver function tests and HBV DNA levels during pregnancy.

2.Neonatal Prophylaxis: Administer hepatitis B immunoglobulin (HBIG) and the first dose of the hepatitis B vaccine within 12 hours of birth. Complete the 3-dose vaccine series by 6 months of age.

3.Breastfeeding: Hepatitis B infection is not a contraindication to breastfeeding. It is safe for HBsAg-positive mothers if the infant receives prophylaxis.

Management of the Mother

Acute Hepatitis B: Supportive care during pregnancy; antiviral therapy may be considered in severe cases.

Chronic Hepatitis B: Assess maternal viral load and liver function to guide the need for antiviral therapy.

Complications of Perinatal Transmission

1.Neonatal: 90% risk of developing chronic hepatitis B if infected at birth. Increased risk of liver cirrhosis and hepatocellular carcinoma later in life.

2.Maternal: Risk of hepatitis B exacerbation postpartum, especially in mothers with high viremia.

Summary: Perinatal transmission is the most common route of HBV infection in high-prevalence areas. High maternal viral load and HBeAg positivity are key risk factors for transmission. Neonatal prophylaxis with HBIG and hepatitis B vaccine is 95% effective in preventing transmission. Antiviral therapy, such as tenofovir, may be needed in mothers with high HBV DNA levels to further reduce transmission risk. Regular screening, timely prophylaxis, and close follow-up are critical to preventing chronic HBV infection in infants.

Superpoint: Hepatitis B transmission in pregnancy can be effectively prevented through maternal screening, antiviral therapy for high viral loads, and neonatal prophylaxis with HBIG and the hepatitis B vaccine, reducing the risk of chronic infection in the newborn.

SUPERFormula: Hepatitis B virus (HBV) is transmitted from mother to child during pregnancy or delivery + Risk of transmission increases with high maternal viral load (>200,000 IU/mL) and HBeAg positivity + Screening for HBsAg is recommended for all pregnant women + Antiviral therapy (e.g., tenofovir) during pregnancy reduces maternal viral load and transmission risk + Neonatal prophylaxis with HBIG and the first dose of the hepatitis B vaccine within 12 hours of birth is 95% effective + Breastfeeding is safe if the infant receives appropriate prophylaxis + Perinatal transmission without intervention leads to chronic HBV infection in 90% of neonates, increasing their risk of cirrhosis and hepatocellular carcinoma = Hepatitis B Transmission in Pregnancy

References: 

Greenberger’s CURRENT Diagnosis & Treatment Gastroenterology, Hepatology, & Endoscopy, 4e

Sonia Friedman, Richard S. Blumberg, John R. Saltzman

Current Medical Diagnosis & Treatment 2024. Maxine A. Papadakis, Stephen J. McPhee, Michael W. Rabow, Kenneth R. McQuaid, Monica Gandhi