Introduction
Hepatitis B, the most common life-threatening liver infection, is caused by the Hepatitis B virus. It is the most common form of chronic hepatitis globally. Most chronic cases are transmitted to the child from the mother (mother-to-child transmission). About 15 to 40% of individuals affected by chronic HBV develop complications like liver cirrhosis and cancer, often leading to death. Mother-to-child transmission of HBV infection can either occur during the pregnancy period or during delivery. Taking proper preventive measures, including vaccinations, helps reduce the mother-to-child transmission of HBV. The preventive measures include maternal screening, the use of antiviral drugs for high-risk pregnant mothers infected with HBV, and postexposure preventive measures, which include HBV vaccination.
What Are the Risk Factors for Perinatal HBV Transmission?
HBV transmission in infants and young children takes place through the following routes:
- Perinatal transmission.
- Transmission from infected mother to child- Vertical transmission.
- Transmission from infected household to child- Horizontal transmission.
Hepatitis B virus is a double-stranded virus that belongs to the Hepadnaviridae family. It consists of a viral envelope (that contains HBsAg) and a nucleocapsid core (HBcAg). Regional prevalence and disease severity vary. It is transmitted through body fluids and remains viable on surfaces for a week. A positive HBsAg (hepatitis B surface antigen) indicates an acute or chronic infection. HBsAg is the marker for maternal HBV screening. HBeAg in serum indicates viral replication; it can cross the placenta and cause infection in the infant.
One of the most important risk factors for perinatal HBV transmission is the high level of HBV DNA (Hepatitis B virus DNA) in pregnant women. HBV DNA test helps in determining the viral load in the blood. The HBV replication in embryos from mothers with high-level HBV DNA is higher than in mothers with undetectable HBV DNA levels.
What Are the Different Routes of Mother-To-Child Transmission?
The different routes of mother-to-child transmission are:
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Intrauterine Transmission:
Intrauterine transmission can occur during the early embryonic stage, and transmission can occur through maternal oocytes or sperms. Transmission during the intrauterine period can also occur through maternal blood or placental leakage during the time of early labor (preterm labor).
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Intrapartum Transmission:
The longer the duration of the first stage of labor, the greater the risk of transmission. Transmission through breast milk is controversial. The risk of transmission is greater if there is abrasion on the nipples.
What Are the Clinical Features of HBV Infection?
Acute HBV infection symptoms are similar to those of other types of hepatitis and include:
- Fatigue.
- Nausea.
- Vomiting.
- Low-grade fever.
- Anorexia.
- Myalgia.
Acute HBV symptoms are similar for both non-pregnant and pregnant women. In less than 1% of acute infections, fulminant hepatitis occurs, leading to irreversible liver damage and death.
Chronic infection has three immunologic phases:
- Immune tolerant.
- Immune active.
- Inactive carrier.
The immune tolerant phase is commonly seen in perinatal transmission cases.
What Are the Preventive Measures?
Per the ACIP (Advisory Committee on Immunization Practices) recommendation, pregnant women should be screened for HBsAg at their first prenatal visit. HBsAg-negative pregnant women who are not vaccinated and are at risk of developing infection should be vaccinated during pregnancy.
Women who are at risk of developing infections are:
- Diabetes.
- HIV (Human immunodeficiency virus) infection.
- Chronic liver disorder.
- Renal disease.
- Drug users.
- Having HBsAg positive sexual partner.
The preventive strategies include:
1. Care For HBsAg-Positive Pregnant Women:
As per the ACIP (Advisory Committee on Immunization Practices) recommendation, all pregnant HBsAg-positive women receive management for chronic HBV infection.
2. Decontaminating Newborn:
Bathing the newborn with mild soap and water helps remove body fluids and HBV-contaminated blood and thus aids in minimizing the risk of infection.
3. Post-exposure Prophylaxis:
Post-exposure prophylaxis involves the administration of hepatitis B vaccination within twelve hours of birth and completing the vaccination series. High maternal HBV DNA (deoxyribonucleic acid) levels and maternal HBeAg positivity, not completing the vaccine series, and delay in timely administration of the Hepatitis B birth dose increase the failure of post-exposure prophylaxis.
4. Antiviral Prophylaxis:
Lamivudine is commonly used for antiretroviral prophylaxis against HBV infection. It acts against HBV replication. Telbivudine is another antiviral used for prophylaxis and is a thymidine nucleoside analog.
5. HBV Screening During Pregnancy:
Along with other routine screening tests done during the first prenatal visit, HBV screening should also be done. It is recommended to be carried out in all pregnant women, whether they have received a vaccination or have done previous tests. Screening is the most important factor that helps control HBV transmission. The screening test is extremely important because the perinatal transmission rate is very high. It helps identify pregnant women who require antiviral therapy and newborns who need prophylaxis.
6. Mode of Delivery:
There is no clear evidence of a relationship between the mode of delivery and the risk of HBV transmission from mother to baby. Some studies have shown that ECS (elective caesarian section) is more favorable than vaginal birth as the risk of transmission is comparatively lower in ECS.
7. Low-Birth Weight Babies:
In preterm infants and low birth weight infants whose weight is less than 4.4 pounds, the first dose of the HBV vaccine is deferred until two months of age. In cases where maternal screening was not done, or the mother was HBsAg positive, the first HBV dose should be administered at birth, and four HBV vaccine doses should be given. Only in the case of low-risk infants should the dose be deferred.
8. Breastfeeding:
Most studies suggest no significant increase in the risk of HBV transmission in breastfed infants, and the risk is further reduced with immunoprophylaxis.
9. Neonatal Management:
Immunoprophylaxis administration in newborns reduces the risk of HBV transmission. Hepatitis B immunoglobulin and HBV vaccination should be administered within a day after birth, followed by timely vaccine doses. Though the usual route of HBV vaccine administration is intramuscular, studies have shown that the intradermal route may increase immunogenicity.
Conclusion
Having an HBV infection while pregnant can pose a serious risk to the baby. The chronicity rate is higher for perinatal infections when compared to adult transmission. Proper maternal screening and preventive measures play a significant role in reducing the perinatal transmission of HBV.
