Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the complications of Urine Blockage in Newborns ?
    ### Response:
    When a defect in the urinary tract blocks the flow of urine, the urine backs up and causes the ureters to swell, called hydroureter, and hydronephrosis.
                
Hydronephrosis is the most common problem found during prenatal ultrasound of a baby in the womb.
    