You review a 31-year-old patient who is 14 weeks pregnant. She is worried as she was exposed to chickenpox two days ago. She cannot remember whether she has had chickenpox as a child.

1. If the mother were to contract chickenpox, what would the principal risk to the foetus be?
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Varicella can cause serious complications in pregnant women. The risk of the foetus being affected is around 1% if the mother develops varicella in the first 28 weeks of pregnancy. The result is foetal varicella syndrome (FVS), which is characterised by eye defects, limb hypoplasia, skin scarring and neurological abnormalities.

2. Which investigation should be organised?
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Any pregnant woman who has not had chickenpox or who is found to be seronegative for VZV IgG should be advised to minimise any contact with chickenpox and shingles and to seek medical help immediately if exposed.

If a pregnant woman is exposed, the first course of action is to perform a blood test and check for VZV immunity. If she is not immune and the history of exposure is significant, she should be given VZV immunoglobulin as soon as possible. It is effective up to 10 days after being exposed.

3. Give two potential maternal complications of chickenpox in pregnancy.
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A pregnant woman that develops chickenpox should seek medical help urgently. There is an increased maternal risk of pneumonia, encephalitis and hepatitis, as well as a 1% risk of developing FVS.

Acyclovir should be used with caution before 20 weeks gestation but is recommended after 20 weeks if the woman presents within 24 hours of the onset of the rash.