Both chickenpox and shingles are caused by varicella-zoster virus (VZV) (human herpesvirus 3):

• Chickenpox = primary VZV infection 
• Shingles (herpes zoster) = reactivation of VZV from sensory nerve root ganglia, following primary infection

Maternal consequences:

• Pneumonia
• Hepatitis
• Encephalitis 

Fetal / baby consequences:

• Spontaneous miscarriage (only in 2nd and 3rd trimester)
• Fetal varicella syndrome (FVS)Characterised by 1 or more of the following: - Skin scarring - Eye defect (microphthalmia / chorioretinitis / cataracts) - Limb hypoplasia - Neurological defect (microcephaly / cortical atrophy / mental retardation / bladder and bowel sphincter dysfunction)

The risk for FVS is highest if exposure is <20 weeks gestation​​​​​​.

Step 1: determine VZV immunity status

• If the patient is uncertain or has no previous history of chickenpox → serology testing for VZV antibodies
• If patient had previous chickenpox or +ve serology → immune to VZV → no further action (note this is not explicitly stated in the guidelines)

Step 2: treat pregnant women that is NOT immune to VZV and has signifiant exposure with PEP (post-exposure prophylaxis)

Choice of PEP:

• 1st line: oral aciclovir / valaciclovir to be given 7-14 days post-exposure
• 2nd line: IM VZIGVaricella-zoster immunoglobulin to be given within 10 days post-exposure

• Symptomatic treatment and hygiene - to prevent secondary bacterial infection

Anti-viral therapy

• Severe chickenpox → IV aciclovir
• If present <24 hours after rash onset → oral aciclovir
  • RCOG states offer if >20 weeks gestation, and consider if <20 weeks gestation

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.