Chickenpox is caused by the varicella zoster virus. Chickenpox is highly infectious and can be dangerous to your baby. If you had chickenpox as a child, it is likely that you are immune; you do not need to worry. If you are unsure whether you have had chickenpox before, you may be offered a blood test to confirm your immunity. If you think you may have come into contact with someone with chickenpox and you know that you are not immune, please phone your GP or midwife for advice. Do not attend the maternity unit for advice unless advised to by your midwife/doctor.