ILLUSTRATION: KIMBERLY MARTENS FOR OBG MANAGEMENT
Hepatitis B is one of the more common infections encountered in the daily practice of obstetrics. It is responsible for 40% to 45% of all cases of viral hepatitis.1,2 Hepatitis B may cause serious complications in both the infected mother and neonate.
In this article, I review the virology, epidemiology, and clinical presentation of hepatitis B and then discuss the key diagnostic tests and, subsequently, the clinical management for both the mother and neonate. I focus particular attention on relatively new information about the value of specific antiviral medication to enhance the protective effect of conventional neonatal immunoprophylaxis.
To set the framework for the discussion, consider the following 2 case studies.
CASE 1 Undetectable level of hepatitis B surface antibody in a pregnant woman
A 25-year-old healthy primigravid woman at 10 weeks’ gestation had a series of laboratory studies that included a test for hepatitis B surface antigen (HBsAg) and hepatitis B surface antibody (HBsAb). The test for the surface antigen was negative. The test for the surface antibody was below the level of detection. Upon questioning, the patient indicates that she received the 3-dose hepatitis B vaccine when she was age 13 years.
- What treatment, if any, is indicated for this patient?
- What treatment is indicated for her neonate?
CASE 2 Pregnant woman tests positive for hepatitis B surface antigen
A 31-year-old woman (G3P2002) at 12 weeks’ gestation tested positive for HBsAg. She indicates that she never has had symptomatic hepatitis and that she considers herself to be in excellent health.
- What additional laboratory tests are indicated at this time?
- What additional laboratory test should be performed at the end of the second trimester?
- What treatment is indicated for the mother and neonate?
Virology and epidemiology of hepatitis B
Hepatitis B is caused by a double-stranded, enveloped DNA virus. The virus has 10 genotypes and 24 subtypes.3 The organism contains 3 major antigens. Detection of these antigens and their corresponding antibodies is an essential step in the diagnostic workup of patients who may be infected.
The surface antigen (HBsAg) confers infectivity and is the most valuable serologic marker of infection. The e antigen (HBeAg) is not present in every infected patient. It is secreted from infected cells, but it is not incorporated into the viral particle. When present, it denotes a high level of viral replication and exceptionally high infectivity. The core antigen (HBcAg) is a valuable serologic marker for distinguishing between acute and chronic infection.1-3
Hepatitis B is highly infectious, much more so than HIV or hepatitis C. The virus has an incubation period of 4 weeks to 6 months, and the duration of incubation is inversely related to the size of the viral inoculum. The virus is transmitted in 3 principal ways: sexual contact with contaminated genital tract secretions, contact with infected blood from sharing contaminated drug-injecting paraphernalia or from receiving a blood transfusion (extremely rare today), and transmission from an infected mother to her neonate. Perinatal transmission occurs primarily during the delivery process as opposed to transplacental infection. Transmission also can occur by more casual household contact, such as sharing eating utensils, kissing, and handling an infant.1,2,4,5
Worldwide, more than 400 million people have chronic hepatitis B infection. In the United States, approximately 1.25 to 1.5 million individuals are infected. Several groups are at particularly high risk for being infected, including1-3:
- Asians
- Alaska Natives
- sub-Saharan Africans
- sex workers
- intravenous drug users
- individuals with hemophilia
- international travelers
- staff and residents of long-term care facilities
- tattoo recipients.
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