Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Twin twin transfusion syndrome ?
    ### Response:
    Twin-to-twin transfusion syndrome is a rare condition that occurs when blood moves from one identical twin (the donor twin) to the other (the recipient twin) while in the womb. The donor twin may be born smaller, with paleness, anemia, and dehydration. The recipient twin may be born larger, with redness, too much blood, and increased blood pressure, resulting in an increased risk for heart failure.
    