Maternal infections

Published on 03/06/2015 by admin

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CHAPTER 26 Maternal infections

Garry Inglis, Mark Davies, David Cartwright

Viral disorders

Hepatitis B

Mothers who are positive for hepatitis B surface antigen (HBsAg) are at risk of passing the virus to their infants (risk 5–20%). The risk is estimated to be between 70% and 90% if they also have the hepatitis B e antigen (HBeAg).

The time of most risk for the infant is the birth process, when the infant comes into contact with maternal blood and secretions. Antenatal transmission is very rare. Infants who acquire hepatitis B have >90% chance of chronic infection.

Prophylaxis

• For babies born to HBsAg-positive mothers, the generally accepted approach is to give the baby hepatitis B immunoglobulin (100 IU, intramuscular, in Australia) as well as the hepatitis B immunisation in the opposite limb. Immunoglobulin should ideally be given before 12 hours of age. This regimen results in >90% protection.

• Before commencing the above schedule, it should be discussed with the parents, or at least the mother, when possible. However, if the mother is unavailable (e.g. after a general anaesthetic), the immunoglobulin should be given anyway. This is just as important as treating pneumonia with antibiotics.

• Serology testing of the infant should not be done before 9 months of age.

• Breastfeeding is not contraindicated.

Immunisation

The most effective way of preventing hepatitis B infection is immunisation prior to exposure to the virus. Routine immunisation in infancy has been introduced in some countries.

• In Australia, this begins at birth and the dose is 5 μg, given by intramuscular injection. Other countries use 10 μg.

• Immunisation should be administered in hospital prior to discharge (when the baby is ‘physiologically stable’) and preferably in the first 24 hours of life.

Babies admitted to our intensive care nursery are deemed to be ‘physiologically stable’ at the time of their discharge/transfer from intensive care. These babies could be going to the postnatal ward, to another hospital, or to the special care nursery. For those admitted to our special care nursery the immunisation will be given when ‘physiologically stable’ as decided by the medical staff.

• The rate of seroconversion following primary immunisation in children is close to 100%, therefore serology testing is not required.

Note that for babies born in Australia at <32 weeks gestational age (GA), hepatitis B immunisation will not be given until the first general immunisation time at 2 months of age, except to those whose mothers are HBsAg-positive for whom hepatitis B vaccination will be given as per the program for term infants.

Some countries adopt a risk-based approach to immunisation, where babies are offered hepatitis B immunisation if they fall into high-risk populations such as certain ethnic groups, or those whose mothers have a history of intravenous drug use.

Hepatitis C virus (HCV)

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