A baby's kidneys usually mature quickly after birth, but problems balancing the body's fluids, salts, and wastes can occur during the first four to five days of life, especially in babies less than 28 weeks gestation. During this time, a baby's kidneys may have difficulty:

  • filtering wastes from the blood so that substances like potassium, urea, and creatinine (among others) are kept in proper balance;
  • concentrating urine -that is, getting rid of wastes from the body without excreting excess fluids; and
  • producing urine -this can be a problem if the kidneys were damaged during delivery or if the baby was without oxygen for a prolonged period of time.

Because of the potential for kidney problems, NICU staff carefully record the amount of urine a baby produces and test the blood for levels of potassium, urea, and creatinine. Staff must also be watchful when giving medications, especially antibiotics, to make sure that the medicines are excreted from the body. If problems arise with kidney function, staff may need to restrict the baby's fluid intake or give more fluids so that substances in the blood are not overly concentrated.