Hepatitis B

Testing in pregnancy allows arrangements to be made for vaccinating the newborn if the mother is found to have hepatitis B.

34.1 Background

Hepatitis B virus is a global acute and chronic communicable disease that causes major hepatic disease (Beasley & Hwang 1984). The virus has an incubation period of 6 weeks to 6 months and is excreted in various body fluids including blood, saliva, vaginal fluid and breast milk. These fluids may be highly infectious. Adults who have hepatitis B may have no symptoms. After infection, some people do not clear the virus; they become carriers and may infect other people.

34.1.1 Hepatitis B in Australia

• Rates of notification of hepatitis B: The notification rate for hepatitis B has declined by 17% in the past 10 years (from 33.0 to 27.4 per 100,000). Rates have been consistently higher among males than females, and were 29.9 and 24.8 per 100,000 in 2016, respectively (The Kirby Institute 2017a). In 2016, the age-standardised notification rate of newly diagnosed hepatitis B infection among Aboriginal and Torres Strait Islander women was 1.2 times as high as that for non-Indigenous women (25.3 vs 20.5 per 100,000) (The Kirby Institute 2017b).
• Age: Among women, the hepatitis B notification rate in 2016 was highest in the 30–39 age group (57.0 per 100,000) followed by the 25–29 age group (47.0 per 100 000) but, in the latter group, declined by 45% (from 85.0 per 100,000 in 2007). The hepatitis B notification rates also decreased in the 0–14, 15–19 and 20–24 age groups by 50%, 38% and 54% respectively. Rates have been stable in the 30–39 age group over the past 10 years (The Kirby Institute 2017a).
• Geographical distribution: The notification rate for hepatitis B infection in Australia has consistently been highest in the Northern Territory, but declined by 64% between 2007 and 2016 (from 118.7 to 43.1 per 100,000) (The Kirby Institute 2017a). In most other jurisdictions, the rate of hepatitis B diagnosis has fluctuated over this period, with small declines in New South Wales (19%, 38.3 to 31.1 per 100,000), Victoria (18%, 37.4 to 30.5 per 100,000) and Western Australia (10%, from 28.9 to 26.1 per 100,000).
• Country of origin: The prevalence of hepatitis B carriage varies between and within countries ATAGI 2009. Carrier rates vary from 0.1–0.2% among Caucasians in the United States, northern Europe and Australia, 1–5% in the Mediterranean countries, parts of eastern Europe, China, Africa, Central and South America, and greater than 10% in many sub-Saharan African, south-east Asian and Pacific island populations Mast et al 2004, Wood et al 2005, Clements et al 2006. First-generation immigrants usually retain the carrier rate of their country of origin, but subsequent generations show a declining carrier rate irrespective of vaccination (Mast et al 2004).
• Risk factors: Routes of transmission of hepatitis B virus include sharing injecting equipment (such as occurs in injecting drug use), needle-stick injury and sexual contact ATAGI 2009. Based on reported cases, hepatitis B transmission in Australia in 2015 continued to occur predominantly among people with a recent history of injecting drug use (The Kirby Institute 2016).
• Hepatitis B in pregnancy: A retrospective cohort study (n=14,857) found around 2% of women to HbsAg positive (Guirgis et al 2009). A prevalence study in the NT found 3.7% of Aboriginal and Torres Strait Islander women and 0.98% of non-Indigenous women to be HbsAg positive (Schultz et al 2008).

34.1.2 Risks associated with hepatitis B in pregnancy

Mother-to-child transmission occurs frequently either in the uterus, through placental leakage, or through exposure to blood or blood-contaminated fluids at or around the time of birth (Lee et al 2006). Perinatal transmission is believed to account for 35–50% of hepatitis B carriers (Yao 1996).

The risk of perinatal transmission is associated with the hepatitis B envelope antigen (HbeAg) status of the mother. If a woman is both hepatitis surface antigen (HbsAg) and HbeAg positive, 70–90% of her children will develop hepatitis B Stevens et al 1975, Akhter et al 1992. If the mother is HbsAg positive but HbeAg negative, the risk is reduced Okada et al 1976, Beasley et al 1977, Beasley et al 1983, Nayak et al 1987, Aggarwal & Ranjan 2004. In a cohort study of HbsAg-positive, hepatitis B DNA-positive women in Sydney (n=313) (Wiseman et al 2009), transmission rates were 3% among hepatitis B DNA-positive women overall, 7% among HbeAg-positive mothers and 9% among women with very high hepatitis B DNA levels.

It has been estimated that people who are chronic carriers of HbsAg are 22 times more likely to die from hepatocellular carcinoma or cirrhosis than noncarriers (95%CI 11.5 to 43.2) (Beasley & Hwang 1984).

34.2 Testing for hepatitis B infection in pregnancy

Testing of all pregnant women for hepatitis B is recommended in the United Kingdom NICE 2008 and the United States Mast et al 2005, Lin & Vickery 2009, USPSTF 2009. The Australian Immunisation Handbook, while making recommendations on vaccination rather than testing, notes that routine antenatal testing for hepatitis B allows appropriate measures to be implemented to prevent newborn infants developing chronic HBV infection ATAGI 2017.

Testing of all women is supported by the findings of observational studies into selective testing:

• testing using risk factors to identify ‘high-risk’ women for HbsAg would miss about half of all pregnant women with HbsAg infection (Summers et al 1987)
• of women offered examination for hepatitis B at 18 weeks pregnancy (n=4,098), one third of women at risk of hepatitis B were not identified by selective testing (Jensen et al 2003)
• universal testing resulted in an estimated detection of 50 additional pregnant women carrying hepatitis B each year who would not have been detected through selective testing (Cowan et al 2006).

A recent systematic review (Lin & Vickery 2009) found no new evidence on the benefits or harms of testing for hepatitis B infection in pregnant women.

34.2.1 Testing method

Testing of blood samples is the accepted standard for antenatal detection of hepatitis B virus NICE 2008 and consists of stages (Balmer et al 2000) testing for HbsAg and confirmatory testing with a new sample upon a positive result.

34.2.2 Other considerations

Mother-to-child transmission of the hepatitis B virus is approximately 95% preventable by administering vaccine and hepatitis B immunoglobulin to the baby at birth Beasley et al 1983, Nair et al 1984, Wong et al 1984, Lo et al 1985, Xu et al 1985, Sehgal et al et al 1992, Zhu 1997, Lee et al 2006.

While a meta-analysis (n=5,900) found that multiple hepatitis B immunisation injections in women with a high degree of infectiousness in late pregnancy reduced rates of intrauterine transmission (Shi et al 2010), all studies included were carried out in China and the findings may not be applicable in the Australian context.

For women with high viral loads (>log 7 IU/mL), discussion with a hepatologist or hepatitis B specialist and maternal antiviral treatment in the third trimester are considerations.

34.3 Practice summary: hepatitis B testing 

When

Early in antenatal care.

Who

• Midwife
• GP
• obstetrician
• Aboriginal and Torres Strait Islander health worker
• multicultural health worker.

What

• Discuss hepatitis B testing
  Explain that it is important to find out whether a woman has or is carrying hepatitis B because of the risk to the baby. 
• Document and follow-up
  Note the results of hepatitis B testing in the woman’s record and have a follow-up system in place so that the babies of women who are found to have hepatitis B are vaccinated on the day of birth. 
• Take a holistic approach
  If a woman is found to have or be a carrier of hepatitis B, other considerations include counselling, contact tracing, partner testing, testing for other sexually transmitted infections and continuing follow-up. Consider testing other children, depending on circumstances.

34.4 Resources

• Australian Technical Advisory Group on Immunisation (2017 update) Australian Immunisation Handbook. 10th edition. Canberra: Department of Health.