Think you have chickenpox or have been in contact with someone who does? Here we cover everything you need to know about chickenpox and pregnancy.

What is chickenpox?

Chickenpox (also known as varicella) is a highly contagious disease caused by the varicella zoster virus (VZV). Shingles is a type of reactivation of the same virus in a person’s body.

What are the symptoms of chickenpox?

It causes a characteristic rash that forms small, fluid filled and particularly itchy blisters which can spread all over the body. The rash goes through three phases: first raised pink or red bumps; second, blisters; and, thirdly, crusts and scabs. Other signs or symptoms that can appear 1-2 days before the rash are viral illness symptoms such as fever, loss of appetite, headache, tiredness and generally feeling unwell.

What should I do if someone close to me is diagnosed with chickenpox?

The risks of becoming infected with chickenpox in pregnancy depend on the immunity status of the mother. In other words, it depends if you have had chickenpox before or if you had the vaccine in the past. If you are immune, you are unlikely to be affected. Over 90% of UK adults are immune to VZV and therefore getting a chickenpox infection in pregnancy is quite rare.

If you believe you had contact with someone with chickenpox or shingles, you need to contact your GP as soon as possible. Your doctor will assess the significance of the contact (i.e. the chance of the virus being spread to you) and your susceptibility to the virus (previous chickenpox in the past and immunization history). You might have a blood test to confirm if you are immune to chickenpox. As long as you are immune, there is no need to worry.

If you are not immune to chickenpox and you had a significant exposure you will be offered medication called varicella zoster immunoglobulin (VZIG) as soon as possible to prevent you getting infected with chickenpox. This medication is effective when given up to 10 days after contact, therefore it is important to visit your GP as early as possible if you have any concerns. Once you develop the rash, there is no therapeutic benefit of having the VZIG as you are already infected.

During this time, you may be contagious so need to isolate yourself from other pregnant women as well as other people who may be susceptible to the infection. Try not to attend the GP or any antenatal appointments. Call your midwife to let them know that you have been in contact with chickenpox so that they can rearrange any appointments. Last but not least, it is very important to inform the GP or your midwife if you develop a rash.

Chickenpox — what to do if you develop a rash

You should immediately contact your GP and you should avoid contact with potentially susceptible individuals — for example other pregnant women and young babies — until the lesions have crusted over. This is usually about 5 days after the onset of the rash.

Once there is a diagnosis of chickenpox in pregnancy and you are within 24 hours of the onset of the rash you will be offered oral acyclovir if you are beyond 20+0 weeks; if you are before 20+0 weeks oral acyclovir will be considered but not offered as a matter of routine.

Aciclovir is an antiviral medication. Although it is not licensed for use in pregnancy, it is not known to be harmful and therefore it is used by the doctors when required. The manufacturers advise use only when the potential benefit outweighs the risks.

What are the risks of chickenpox in pregnancy for the mother?

Varicella infection can range from a mild condition which can be managed at home, to a more severe form that may include the development of pneumonia, hepatitis and encephalitis. In rare cases it can be fatal. If you experience any of the following, seek medical advice or attend A&E (not the maternity unit where there are other pregnant women and babies):

• Respiratory symptoms (difficulty breathing)
• Haemorrhagic rash or bleeding
• Neurological symptoms (sensitivity to light, drowsiness, severe headache, seizures)
• You are getting progressively worse

If you are a smoker, have a known lung condition or have recently been taking steroids, it’s worth getting some medical advice anyway, even if you feel relatively well.

What are the risks of chickenpox in pregnancy for the unborn baby?

If the baby gets the infection early in the pregnancy, the baby can develop fetal varicella syndrome (FVS). If the baby gets the infection around the time of delivery, the newborn can develop varicella infection of the newborn/neonatal varicella. The symptoms and the implications vary.

Fetal varicella syndrome

If chickenpox occurs in the first trimester (weeks 1-12) of the pregnancy, the risk of miscarriage does not appear to be increased. If the woman develops chickenpox in the first 28 weeks of pregnancy, there is a small risk (approximately 1%) that the baby can get infected and develop fetal varicella syndrome. Therefore, women who develop chickenpox in pregnancy earlier than 28 weeks should be referred to a fetal medicine specialist. A detailed ultrasound scan and examination of a sample taken from the fluid around your baby (amniocentesis) might give more information about how baby is doing.

Fetal Varicella Syndrome (FVS) is characterised by a spectrum of anomalies. The defects can involve the skin (scarring), the eyes (microphthalmia, chorioretinitis or cataracts), the limbs/bones/muscles (hypoplasia) and the nervous system (microcephaly, cortical atrophy, mental retardation or dysfunction of bowel and bladder sphincters) among others.

Varicella infection of the newborn

If maternal infection occurs in the last four weeks of the pregnancy, there is a significant risk of varicella infection of the newborn and you will be reviewed by an obstetrician. The infection may be passed to the baby via the placenta, in the birth canal or directly from you after birth. Unfortunately, there is not enough evidence to support any specific treatment to help prevent chickenpox transmission from the mother to the baby while the baby is still in the womb.

Your obstetrician will advise you as to the best time to deliver the baby to reduce the risk of varicella of the newborn. This is usually at least 7 days after the rash develops. Also, a neonatologist (doctor for the newborn) will be involved and make a plan for the care of the baby once delivered.
Varicella Infection of the Newborn resembles chickenpox symptoms in adults but can be quite severe for the baby, with higher rates of complications. Therefore, babies will receive VZVIG +/- aciclovir soon after delivery.

You can still breast-feed the baby as long as you feel well enough to do so, there are no blisters around the nipple area, and the baby receives prophylactic treatment.

Main Points

• more than 85% of UK adults are immune to chickenpox and therefore chickenpox in pregnancy is rare.
• Contact your GP if you are pregnant and have been in contact with chickenpox or shingles.
• Avoid other pregnant women and young children if you are not immune of if you have symptoms of chickenpox.
• If you develop the rash, you will need aciclovir treatment if you are more than 20 weeks.
• Fetal Varicella syndrome is rare (<1% risk if less than 28 weeks), but can have devastating consequences.
• Getting chickenpox in the last 4 weeks of pregnancy has a high risk of transmission to the baby and delivery should be delayed at least 7 days after the onset of the rash.

 

References
● Chickenpox in Pregnancy RCOG Green Top Guideline No.13
● Guidance on the investigation, diagnosis and management of viral illness, or exposure to viral rash illness in pregnancy, Public Health England 2019
● Mandelbrot, L. (2012), Fetal varicella – diagnosis, management, and outcome. Prenat Diagn, 32: 511-518. doi:10.1002/pd.3843