In this month's edition of the Journal of Obstetrics and Gynaecology Canada, the SOGC released a new clinical practice guideline for the management of varicella infection in pregnancy. Varicella zoster virus (VZV) infection, commonly referred to as chickenpox, is a common childhood disease that can affect the developing fetus if the mother contracts the disease during pregnancy. Here are some of the key points from the guideline that you should be aware of:

Chickenpox in pregnancy: the numbers

• 90% or more of pregnant women are immune to the varicella virus because of childhood exposure or varicella immunization.

• Varicella infection affects 2-3 pregnancies out of 1000 every year. This equates to 700-1050 cases in Canada per year and 8,100-12,100 cases in the US per year.

• Of those pregnant women with an active varicella infection, 5-10% will develop a serious respiratory disease known as pneumonitis. This means approximately 35-105 women in Canada and 405-1210 women in the US will develop pneumonitis each year. Women who develop pneumonitis may need intubation and mechanical ventilation and are at a much higher risk of death.

• VZV can cross the placenta and lead to congenital varicella syndrome (CVS), a condition that results in malformations and deformations such as partial limb reductions. Fetal infection is rare, with a rate of 0.4% prior to 13 weeks gestation and a rate of 2% between 13-20 weeks gestation. There are about 4 cases per year in Canada and 41 cases per year in the US.

• If the mother contracts chickenpox between 5 days before birth and 2 days after birth, the newborn can develop neonatal varicella. Varicella in a newborn can develop into disseminated visceral and central nervous system disease, which is often fatal. Approximately 20-30% of babies born to affected mothers at the time of delivery will develop neonatal varicella and it will be fatal in up to 30% of those infants.

Key Recommendations for Women

• If a woman does not recall having chickenpox as a child, then she should receive the varicella immunization prior to conception or after the birth of her child. The SOGC and AAP recommend waiting at least one month after receiving the immunization before becoming pregnant. However, a pregnancy registry established by the vaccine's manufacturer shows no cases of CVS in the 362 recorded cases of women who conceived within 3 months of receiving the varicella vaccine.

• If a pregnant woman is not immune to VZV, she should seek immediate medical help if she comes in contact with a contagious person. Treatment with varicella zoster immunoglobin (VZIG) will be given to reduce the risk of complications of maternal infection.

• A pregnant woman who contracts chickenpox should be treated with an antiviral drug.

• If a mother contracted chickenpox within 5 days before and 2 days after delivery, then her child should be treated with VZIG to reduce the risk of neonatal varicella.

Recommendations in the SOGC's clinical practice guideline are comparable to recommendations from the Center for Disease Control.

A parent-friendly fact sheet on the topic of varicella vaccination has been created by the Organization of Teratology Information Specialists (OTIS).

Information on other immunizations during pregnancy can be obtained through the Center for Disease Control.

And now for today's question to you, the reader: How will you use this information?

Published: March 22, 2012

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