Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Congenital varicella syndrome ?
    ### Response:
    Congenital varicella syndrome is an extremely rare disorder in which affected infants have distinctive abnormalities at birth  due to the mother's infection with chickenpox (maternal varicella zoster) early during pregnancy (i.e., up to 20 weeks gestation).
    