Chicken Pox and Pregnancy

It is quite often that women who are pregnant come into contact with someone who has chicken pox. This can cause great worry, but it is uncommon for there to be major problems.

80-90% of women who are pregnant are likely to be protected from chicken pox, either from previously having the disease or a sub-clinical, 'silent' infection.

What are the Symptoms of Chicken Pox?

Chicken pox is highly infectious and is spread by droplets through the air and via contact. The infection causes fever, a feeling of generally being unwell and an itchy rash that develops into small vesicles which crust over before healing.

The incubation period is on average two weeks, which means that it can be brewing this long before even showing itself, and a person is infectious (can transmit chickenpox to another person) from two days before the rash appears until after the vesicles crust over.

Risks to the Baby

Firstly, if the mother has definitely had chicken-pox, there is no risk to the baby or her. In any case, even if she doesn't recall having had chicken pox, it is likely she has antibodies (80% do) from a silent (asymptomatic) infection. So if there's any doubt about it, she should see a doctor for a blood test to check if she's immune.

Risks to the baby are important at the following two times, if mum gets chicken-pox:

1. Before 20 weeks - risk of chicken pox syndrome. This is actually quite rare. Up until 14 weeks the risk is about 0.4%, whereas between 14-20 weeks it is 2%. If a woman has VZ-Ig treatment (see below) after being exposed, the risk is even lower.

2. Mum's rash developing within a week before delivery to a month afterwards. It takes about a week for mum to pass the protective antibodies to the baby, so if born before that time, the babe is at risk of overwhelming infection after birth.

Between 20 weeks and term there is no risk to the baby. The other big risk of chicken pox is to the mother. She is much more likely, during pregnancy, to get a chicken pox pneumonia (10%) which can be very severe (even life-threatening).

Getting Treatment

In cases of 'at risk' exposure it is important to give Varicella-Zoster Ig ('man-made' antibodies) to mum and/or baby. This can be lifesaving and significantly reduce the disease severity. It must be given not later than 10 days after exposure.

Remember all of the above ONLY apply if at-risk - ie mum proven not to have antibodies. If in doubt, see your doctor who can do the blood test.