If you haven't had chickenpox before and catch it when you're pregnant, it can make you feel very unwell and some women can develop pneumonia. Depending on how many weeks pregnant you are, chickenpox may affect your unborn baby. If you catch chickenpox in the first 20 weeks of pregnancy, it may, in rare cases, affect your unborn baby. It can affect the development of your baby's arms, legs, brain or eyes, and cause scarring on the skin and poor growth. This is called foetal varicella syndrome. If you get chickenpox after 28 weeks there doesn't seem to be any risk of it causing your baby to develop an abnormality. However, your baby may catch it from you and develop a type of chickenpox called symptomatic varicella infection. This means your baby may be ill when he or she is born.
Attribution: BUPA