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Chickenpox (varicella)

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Chickenpox (varicella)
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Most women are already immune to chickenpox. If you are concerned about your immunity you can have this checked before becoming pregnant. Discuss this with your midwife or family doctor.

If you are exposed to chickenpox in pregnancy and think you are not immune, there is a small risk to your baby, especially if it happens in the middle three months. If you are concerned, advice should be sought immediately from your family doctor. You can have an antibody test and if you are not immune you can take further measures.

What is chickenpox?

Chickenpox is caused by the virus Varicella-zoster. The first symptoms you notice are a fever, a runny nose, cough and tiredness. A day or two later a rash begins, starting as pink blotches but quickly becoming blisters. The blisters last three to four days before turning into scabs and drying out. Most of the rash is over your body, face and scalp. You may have spots in different stages in the same area. The chickenpox rash is sometimes very itchy and scratching can introduce further infection into the blister sores.

References

American Academy of Pediatrics (2000) Varicella vaccine update (RE9941). Pediatrics; 105: 1, 136-141.

Freedman, E. (1998) A minor illness? New Generation; 16-17.

Seidman, D.S., Stevenson, D.K., Arvin, A.M. (1996) Varicella vaccine in pregnancy. British Medical Journal; 313: 701-702.

Further support

The NCT holds a special experiences register to enable mothers to talk to other mothers who have had similar experiences. Contact enquires on 0870 444 8707.

Chickenpox and shingles: are they connected?

Shingles (herpes zoster) can only occur in someone who has had chickenpox. The chickenpox virus can stay active in a person's body for some time after they have had chickenpox. Shingles is what happens when the chickenpox virus becomes activated again. With shingles you notice a rash of blisters just in one place of your body. The shingles rash can be very painful and can make you feel quite ill.

Laboratory studies have not shown problems for the babies of mothers affected by shingles during pregnancy, but there have been some individual reports of congenital defects in babies.

Prevention and treatment

Pregnant women should avoid contact with anyone suspected of being infected. This is especially important if you are not sure whether you have had chickenpox yourself. If you are pregnant and have been in contact with someone with chickenpox then your family doctor will want to check whether you are immune. If you are not then there are options:

i) Varicella-zoster immune globulin (VZIG)
Babies and pregnant mothers can be protected with VZIG antibodies (varicella-zoster immune globulin). This is given to babies up to 28 days old who have been exposed to chickenpox and to mothers who have been exposed and who are not immune (immunity is determined by an antibody test). VZIG is not a chemical drug but is prepared from the screened blood of donors with strong immunity. It is not totally effective as it only makes the attack less serious. It also only protects against chickenpox for a short period of time, not forever because it does not stimulate your body to make its own antibodies. It is a form of 'passive immunisation'. VZIG has to be given within four days of the baby or mother coming into contact with someone with chickenpox.

ii) Varicella vaccine
A live attenuated varicella vaccine was licensed in the USA by the Food and Drug Administration in March 1995. It works by causing your body to produce its own protection (antibodies) against the virus. One dose is injected under the skin, followed by a second dose four to eight weeks later.

The vaccine is 70%-90% effective in preventing chicken pox and more than 95% effective in preventing severe chicken pox. But it cannot be given to a pregnant women because it is live and may cause the mother to become ill. It is also not recommended for use in children under 12 months.

If you are not pregnant having the chickenpox vaccine is much safer than getting chickenpox itself. Most people who receive the chickenpox vaccine do not have any problems. However, there have been cases where adults have become ill with the disease as a result of having the vaccination.

In many parts of the USA the vaccine is routinely used. It is thought to be cost-effective to vaccinate. This is because children miss five to seven days of school or child care, which causes social disruption. Vaccination also reduces the number of pregnant women who are exposed to chicken pox and the potential detrimental effects on them and their babies. Vaccination prevents the rare deaths in children too. So there are arguments for vaccination programmes to get rid of the disease altogether, even though in general it is a very mild infection.

In the UK, the vaccine is available from your family doctor but is not in routine use. The best time to get tested for and get immunised against chickenpox is before pregnancy. If you are not sure whether you have had chickenpox and are thinking about getting pregnant, check with your doctor about having an antibody test. If you are not immune you could choose to have the vaccine. After the full course of the vaccine you have to wait at least one month before trying to get pregnant.

How does chickenpox affect breastfeeding mothers?

Older babies are not endangered by breastfeeding from a mother with chickenpox. The antibodies passed through their mother's milk will help them fight of the infection themselves.

We do not know whether the varicella vaccine virus (see below) passes into breastmilk. Although most medicines pass into breastmilk in small amounts, many of them may be used safely while breastfeeding. Mothers who receive this vaccine and are breastfeeding should discuss this with their doctor.

What effects does chickenpox have on the unborn child?

Remember chickenpox in pregnancy is very rare. In 1993 it was estimated that about three in 1,000 pregnant women in the UK caught chickenpox. Infection during the first three months of pregnancy carries a low risk of damage to the foetus (less than 0.5% risk). Infection during the second trimester carries the highest risk (2% risk). Mothers who become ill during the third trimester produce antibodies that cross the placenta and protect the baby. It may be that foetal deaths are due to maternal fever rather than direct infection.

There is a much lower risk of damage to the unborn baby due to chickenpox than rubella (German measles), which causes damage to about 85% of babies whose mothers are infected during pregnancy.

Where a mother contracts chickenpox, the result may be miscarriage or the baby may develop 'congenital varicella syndrome'. Here the baby has malformations like those caused by German measles. These may be brain damage, birth defects involving the arms and legs, digestive or genito-urinary problems, eye infections, scarring of the skin, or poor growth.

What effects does chickenpox have on newborn babies?

If the mother contracts chickenpox seven days before she gives birth or within 28 days after birth, there is a risk of the baby contracting neonatal chickenpox, which can have serious consequences. Some studies have estimated mortality rates to be as high as 20%-30% in babies who contract chickenpox within a few days of birth.

The effects of chickenpox on the pregnant mother

Chickenpox is considerably more serious in adults than children. Only 2% of cases occur in people over 20, but these account for 25% of the deaths from chickenpox. In pregnant women the disease is particularly severe. This is because your hormone levels are up and your immune system is less active. A few mothers (about 10%) who contract chickenpox have chest and breathing complications (pneumonia). Of these mothers, about 40% die. Infection or suspected infection should be taken very seriously. Medical advice is that women should take Aciclovir immediately to minimise risks of respiratory infection. The drug must be used with caution for pregnant or breastfeeding women, so it is important to ensure that your symptoms are chickenpox.

Are you immune?

If you can remember having chickenpox there is at least a 97% chance that you are immune. Even among those who can not remember having chickenpox about 80% are immune. You can have a blood test taken if you are not sure. This can be done before or after conception. It is thought that about 95% of women are immune before they get pregnant. But recent studies suggest that this figure is dropping slightly.

How easy is it to catch chickenpox?

Chickenpox is very infectious: 60 per cent to 90 per cent of people who aren't immune will become infected after coming in contact with a person in the infectious stage of the illness. The virus is passed through close contact. The fluid in the blisters of the rash is full of chickenpox viruses, it can therefore be spread by close person-to-person contact. Someone with chickenpox is infectious to others for two days before the rash shows. They stay infectious until the blisters disappear and dry scabs form. This takes four or five days.

Chickenpox can be spread by coughing and sneezing. This is because the chickenpox virus is found in the secretions in a patient's nose and mouth. The dry scabs are not infectious. Shingles blisters also contain the virus, so a person who has never had chickenpox can become infected with chickenpox from someone who has shingles.

Someone with chickenpox is most infectious one or two days before their spots appear. This makes it difficult to avoid infection. It usually takes between two and three weeks from being infected with chickenpox until you become ill. The illness usually lasts about five days.

Treatment

In pregnancy, any drug treatment should be given only under a doctor's supervision. Paracetamol is useful for bringing your temperature down. Do not use aspirin. Aspirin use during a viral illness, particularly chickenpox, has been associated with a risk of developing Reye's syndrome.

The drug Aciclovir (available only from a doctor) is used to treat the symptoms of chickenpox. Aciclovir can be given to a baby from three months officially - in practice it would probably be given to a baby before the three months if it was really ill. It is usually only given to teenagers and adults, because the disease is more severe in that age group and the drug can have side-effects. The drug should help reduce the severity of chickenpox symptoms. It works best if you start taking it within 24 hours of the rash's first appearance. The other drugs that can be used are famciclovir and valaciclovir.