Among viral hepatitis infections, hepatitis B is considered the most serious. Both children and adults can be infected with the hepatitis B virus; however, neonatal infection is associated with particularly severe consequences and a high risk of long term complications.
Etiology of hepatitis B in neonates
In Vietnam, epidemiological data indicate that approximately 10 to 13% of pregnant women are infected with the hepatitis B virus, representing a significant public health concern. Vertical transmission from mother to child during pregnancy and perinatal periods is the primary route of infection in neonates and poses substantial clinical risks.
The likelihood of mother to child transmission varies depending on the stage of pregnancy. If maternal infection occurs during the first trimester, the transmission rate is approximately 1%. This risk increases to around 10% during the second trimester and rises significantly to 60 to 70% during the third trimester.
Assessment of hepatitis B viral activity and infectivity is commonly performed through serological testing, particularly the detection of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg), which are widely available in standard hospital laboratories.
Clinical data indicate that if a pregnant woman tests positive for both HBsAg and HBeAg during the third trimester, the risk of vertical transmission can reach 90 to 100%. In contrast, if only HBsAg is positive while HBeAg is negative, the transmission risk is considerably lower, estimated at approximately 20%.

Clinical severity of hepatitis B in neonates
Neonatal hepatitis B infection acquired through vertical transmission from the mother remains a significant clinical challenge. Approximately 5 to 7% of infected neonates may develop acute hepatitis B.
In most cases, acute hepatitis B in neonates presents with nonspecific or subtle clinical manifestations, often lacking typical symptoms, which makes early recognition difficult.
Some infants may exhibit signs such as jaundice, dark urine, and poor feeding. Laboratory investigations typically reveal markedly elevated liver enzymes and increased serum bilirubin levels. However, these signs are frequently overlooked, as neonates are often observed in low lighting conditions, making jaundice difficult to detect. Additionally, these manifestations may be misinterpreted as physiological neonatal jaundice, leading to delayed medical evaluation.
Importantly, up to 50% of neonates infected with hepatitis B virus from their mothers may progress to chronic hepatitis B, significantly increasing the risk of long term complications, including liver cirrhosis and hepatocellular carcinoma in adulthood.
Management and prevention of hepatitis B
When a neonate is suspected of hepatitis B infection, prompt medical evaluation at a healthcare facility with appropriate diagnostic capabilities is essential. Once the diagnosis is confirmed, caregivers should strictly adhere to the physician’s recommendations. Even if clinical signs such as jaundice improve or resolve, the infant should undergo regular follow up examinations, typically on a monthly basis for approximately six months.
For neonates without hepatitis B infection, timely immunization is critical. The first dose of the hepatitis B vaccine should be administered within 24 hours after birth. This should be followed by the second dose one month later and the third dose at two months of age, in accordance with the recommended vaccination schedule.

For women who test negative for hepatitis B virus infection, vaccination should be administered promptly following screening.
For women who are carriers of hepatitis B virus and are planning pregnancy, consultation with a hepatology or infectious disease specialist is essential to receive appropriate preconception guidance.
Pregnant women who have not been vaccinated and are diagnosed with hepatitis B during pregnancy should seek specialist consultation for optimal clinical management, particularly if infection occurs from the second trimester onward.
For couples in which both partners are not infected with hepatitis B virus, vaccination is strongly recommended to ensure safety prior to conception. In cases where one partner is infected, the uninfected partner should receive hepatitis B vaccination as soon as possible.
Note: The information provided in this article by Hong Ngoc General Hospital is for reference purposes only and does not substitute for professional medical diagnosis or treatment. Patients should not self medicate. To obtain an accurate diagnosis and appropriate treatment plan, individuals are advised to visit a healthcare facility for direct examination and consultation with a qualified physician.
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