Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Anencephaly ?
    ### Response:
    Anencephaly is a type of neural tube defect characterized by abnormal development of the brain and the bones of the skull. The neural tube is a narrow channel that normally folds and closes between the 3rd and 4th weeks of pregnancy, forming the brain and spinal cord of the embryo.
    