Important: This is intended as general information only. It may not apply to your specific situation. It is not a substitute for medical advice. If you have a question or concern, please raise it with me at your next appointment or contact me sooner if it's urgent.
Chickenpox in Pregnancy
Infection with chickenpox (or Varicella Zoster Virus) in pregnancy is unusual these days because most adults are immune (from having had the infection as a child) and there is less chickenpox around, thanks to vaccination. Once you’ve been infected with (or vaccinated against) the virus, you become immune (as measured by antibodies in your blood) and cannot be reinfected. However, the virus never really goes away. It lies dormant within the body and can reactivate in localized areas – known as shingles.
Chickenpox is spread by respiratory droplet and people are most infectious just before they come out in the classic chickenpox rash. That is, before it becomes obvious that they have chickenpox, which makes it hard to avoid – one of the many reasons why vaccination is so important. It is also possible to become infected by contact with the fluid in the vesicles (blisters) of the rash although this is less common. The vesicles that form in the rash of shingles may also be infectious although much less so.
Effects of chickenpox on the fetus
Generally speaking, chickenpox is much more of a concern for the mother than the baby. However, if infection occurs in the first trimester, damage to the baby can result. The most common problem seen in intrauterine infection is skin scarring. Less commonly, the baby may have limb, eye and brain abnormalities. This syndrome is very uncommon - it is estimated to occur in less that 1% of babies whose mothers are infected in the first trimester. It has only been seen with infections occurring before 20 weeks gestation and mostly between 8 and 12 weeks gestation.
Infections that occur after 20 weeks gestation are generally not too much of a problem for the baby – most of the important organ systems have formed by this time and, although the baby may well get the infection, they also get the mother’s antibodies.
If the mother is infected in the last couple of weeks of the pregnancy, there is a possibility that the baby will be born with an acute infection. This is because it takes about a week for the mother’s antibodies to develop and cross the placenta to deal with the infection. If the baby is born after it has been infected but before the antibodies have had time to develop and work, the baby may still have chickenpox at birth. This situation is unusual and can be treated.
Effects of chickenpox on the pregnant woman
As you may be aware, chickenpox is usually worse in adults than it is in children. This is especially the case for pregnant women who can get a particularly nasty form of chickenpox involving pneumonitis (lung infection) and hepatitis (liver infection). This illness may be severe and can be fatal, and this is the main reason we are so concerned about chickenpox in pregnancy.
Shingles in pregnancy
If a pregnant woman develops shingles in pregnancy, there is no need to worry. Although painful and extremely inconvenient, the reactivation of the virus is confined to a localized area of the body. The mother is very unlikely to have any serious ramifications and there is no risk to the baby.
What to do if you are exposed to chickenpox while pregnant
I will test you at your first antenatal visit to see if you are already immune to chickenpox (most people are). If you are, then you have nothing to fear as you cannot be reinfected. The only way for the fetus to become infected is if you are infected first so the baby is completely protected.
If you are not already immune (ie if you are susceptible to infection), I will discuss this in detail with you.
If you are susceptible to chickenpox and are exposed to the virus, I can give you an injection of Varicella Zoster immunoglobulin (VZIG - antibodies specific to chickenpox). This makes it much less likely that you will become infected with the virus. VZIG does not help if the rash has already developed. If the rash has already developed, I can treat you with a drug called Aciclovir which may make the resulting illness less severe.
If you think you have chickenpox, please call me but don’t come into the rooms. The rooms are usually full of other pregnant women and we need to avoid exposing them to the virus. I will arrange for you to be treated without coming into the rooms.
What to do if you are exposed to shingles while pregnant
The same rules apply. If you are already immune to chickenpox, you cannot become infected from shingles. In any case, the risk of infection from shingles is very low as you can really only get it from direct contact with the rash. Depending on the exposure, we sometimes give VZIG to susceptible women who have been exposed to shingles.
What to do if your newborn baby is exposed to chickenpox or shingles
Obviously, it would be best to avoid this situation so if someone you know has chickenpox, they should stay away. Sometimes this isn’t possible - for example if your baby’s older sibling has the virus or if someone who visited you yesterday has developed the rash today. If you are known to be immune, the risk to the baby is low as your antibodies will have crossed the placenta and remain in the baby’s circulation for a few weeks. If you are not immune, we generally give the baby VZIG. If this situation arises, you should call me, your GP or your baby’s paediatrician.