Chickenpox exposure in pregnancy
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Background
Chickenpox is caused by primary infection with varicella zoster virus (VZV). VZV is a DNA virus of the herpes family that is highly contagious and transmitted by respiratory droplets and by direct personal contact with vesicle fluid or indirectly via fomites. Shingles is reactivation of dormant virus in dorsal root ganglion. In pregnancy there is a risk to both the mother and also the fetus.Incubation and infectivity
The incubation period is considered to be between 1 to 3 weeks. VZV disease is infectious from 48 hours prior to the rash appearing until the vesicles have crusted over (typically within 5 days of vesicle appearance)Risks
Risks to the mother- 5 times greater risk of pneumonia
- Increased risk of hepatitis and encephalitis
Fetal varicella syndrome (FVS)
- risk of FVS following maternal varicella exposure is around 1% if occurs before 20 weeks gestation
- studies have shown a very small number of cases occurring between 20-28 weeks gestation and none following 28 weeks
- features of FVS include skin scarring, eye defects (microphthalmia), limb hypoplasia, microcephaly and learning disabilities
Other risks to the baby
- If maternal infection occurs in the last 4 weeks of a woman’s pregnancy, there is a significant
are infected and approximately 23% develop clinical varicella
- Severe neonatal varicella is more likely if the mother develops rash between 7 days before and 7 days after birth which may be fatal to the newborn child in around 20% of cases.
- Maternal chickenpox infection between 28 and 36 weeks of pregnancy may result in the baby developing shingles in the first few years of his or her life.
Management of chickenpox exposure:
- if there is any doubt about the mother previously having chickenpox maternal blood should be urgently checked for varicella antibodies
- if the pregnant women is not immune to varicella she should be given Post Exposure Prophylaxis (PEP).
- Previously varicella zoster immunoglobulin (VZIG) was advised as first line for VZV PEP but updated guidance in 2024 now recommends antivirals (see box below)
If the pregnant woman is not immune to VZV and she has had a significant exposure, she should be offered Post Exposure Prophylaxis (PEP). Oral antiviral therapy i.e. aciclovir (or valaciclovir) is recommended as the first choice for PEP by the UKHSA. It should be given from Day 7 to 14 post exposure.
When there is a contraindication or adverse effects to antivirals, varicella zoster immunoglobulin (VZIG) may be considered as PEP. It should be given as soon as possible post-exposure. VZIG is effective when given up to 10 days after contact.
Significant exposure is defined as contact with someone with chickenpox in the same room for 15 minutes or more, face-to-face contact or contact in the setting of a large open ward. Herpes zoster shingles also poses a risk if it is disseminated or it occurs in an exposed area of the body (e.g. ophthalmic shingles) or in an immunocompromised individual where viral shedding may be greater.
When there is a contraindication or adverse effects to antivirals, varicella zoster immunoglobulin (VZIG) may be considered as PEP. It should be given as soon as possible post-exposure. VZIG is effective when given up to 10 days after contact.
Significant exposure is defined as contact with someone with chickenpox in the same room for 15 minutes or more, face-to-face contact or contact in the setting of a large open ward. Herpes zoster shingles also poses a risk if it is disseminated or it occurs in an exposed area of the body (e.g. ophthalmic shingles) or in an immunocompromised individual where viral shedding may be greater.
Management of chickenpox rash in pregnancy:
- consensus guidelines suggest oral aciclovir should be given if pregnant women with chickenpox present within 24 hours of onset of the rash
- intravenous aciclovir should be given to all pregnant women with severe chickenpox
- women should avoid contact with potentially susceptible individuals, e.g. other pregnant women and neonates, until the lesions have crusted over. This is usually about 5 days after the onset of the rash.
- VZIG has no therapeutic benefit once chickenpox has developed and should therefore NOT BE USED in pregnant women who have developed a chickenpox rash
- VZV vaccination should not be given to pregnant women