Chickenpox is caused by the herpes varicella zoster virus (VZV). VZV is highly contagious and transmitted by respiratory droplets and contact with vesicular fluid. Pregnant women, particularly after 20 weeks’ gestation, are at increased risk of severe chickenpox disease and its complications.
Chickenpox infection during the first and second trimesters can lead to fetal varicella syndrome (FVS). This is characterised by skin scarring, eye defects, hypoplasia of the limbs and neurological abnormalities. There is up to a 2% risk of FVS following maternal infection with VZV during the first 28 weeks of pregnancy.
Perinatal exposure to VZV, particularly with maternal rash onset within seven days of delivery, can result in severe neonatal varicella infection.
The UK Health Security Agency (UKHSA) recommends use of aciclovir or valaciclovir at any stage of pregnancy for treatment of chickenpox, or post-exposure prophylaxis (PEP).
Use of varicella immunoglobulin is not generally recommended in pregnancy due to data suggesting that clinical efficacy is not superior to antivirals. However, it may be used for PEP where aciclovir/valaciclovir are contraindicated.
Live chickenpox and varicella zoster vaccines should be avoided during pregnancy due to the theoretical risk of fetal infection. However, the limited available data provide no evidence of an increased risk of FVS or congenital malformation in the infant following varicella vaccination during pregnancy.
Inadvertent exposure to VZV, immunoglobulin, or vaccination at any stage in pregnancy would not usually be regarded as medical grounds for termination of pregnancy. Chickenpox infection during pregnancy is an indication for referral to a fetal medicine specialist for discussion of the risks of FVS and any required additional fetal monitoring. Other risk factors may also be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.
This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to NHS health care professionals who are logged in.
If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.
If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.