The effects of the varicella virus vaccine on the fetus are unknown; therefore, you should not be vaccinated if you are pregnant. You should also avoid becoming pregnant for 1 month following the vaccine.
If vaccination occurs and you were unknowingly pregnant during that time or if you becomes pregnant within 4 weeks after a Varicella vaccination, there is a theoretical risk for the baby. However, the risk is so small that it should not be regarded as a reason to terminate the pregnancy. Do speak to your health care provider if this occurs.