In the NICU, various tests are important in diagnosing problems and identifying progress in newborns. The following are some of the tests typically performed:

Blood tests: These are among the most frequent procedures done in the NICU. Blood tests provide crucial information on how a baby is doing, and alert doctors to potential problems before they become more serious.

• Blood tests can tell if a baby is anemic or if bilirubin levels are too high. Bilirubin is formed when red blood cells break down. Jaundice occurs when the liver can't remove bilirubin from the blood.
• They show whether a baby has low blood sugar (hypoglycemia), high blood sugar (hyperglycemia), salt or water imbalances, or nutritional needs (such as problems with protein, liver and kidney function)—all of which can cause problems if not corrected.
• Blood tests also can help determine if a baby has an infection and which antibiotic(s) should be used to treat it.
• If a baby is very sick, she may need blood tests several times an hour to measure the levels of blood gases (oxygen and carbon dioxide). This may be done on a blood sample taken from an artery, because arteries carry oxygen to all parts of the body. The sample can be taken through the umbilical catheter, if a baby has one in place, or from an artery in the wrist or foot.

A baby may have a blood test to check blood gases soon after she is admitted to the NICU, to determine whether she needs additional oxygen or mechanical ventilation.

Computed tomography (CAT or CT scan): A CT scan is an advanced form of imaging that often can produce a more precise image than an x-ray or ultrasound examination. It focuses a beam of energy on the part of the body the doctor wants to see, and uses computers to turn it into a full picture (two-dimensional image). The baby will need to be taken to the radiology department and possibly sedated (so he doesn’t move) for this test.

Echocardiogram: A specialized form of ultrasound examination that is used to study the heart. It can detect structural problems (heart defects) and problems with how the heart works.

Hearing test: Premature and other sick babies are at increased risk of hearing problems. Before a premature baby goes home, she probably will have a hearing test called a “brainstem auditory evoked response test.” A tiny earphone will be placed in her ear to deliver sound. Small sensors, which are taped to the baby’s head, will relay information to a machine that measures the electrical activity in her brain in response to sound. Your baby's doctor will discuss the results of the hearing test with you and whether any follow-up will be necessary. It is important to detect hearing problems early, in order to help prevent speech and language problems.

Magnetic resonance imaging (MRI): Like a CT scan, an MRI can produce a very detailed picture that may be difficult to see on an x-ray or ultrasound. The MRI gives a more detailed view than a CT scan, using powerful magnets and computers to create an image. This test is painless and safe for babies, and there are no x-rays involved. A baby will need to be moved to the radiology department for this test.

Newborn screening test: This is a test performed by pricking a baby’s heel to obtain a few drops of blood on a filter paper. It tests babies for serious hereditary disorders. Most states screen for between 3 and 20 disorders (now 17-19 states do greater than 9). New technologies have made it possible to test for even larger numbers of disorders at one time.

Retinopathy of prematurity (ROP) examination: This test usually is done for all babies born before 28-30 weeks gestation, whether or not they have special oxygen needs, and any baby born before 35 weeks who requires oxygen. An ophthalmologist (eye doctor) will examine a premature baby’s eyes four to seven weeks after birth with a special scope (ophthalmoscope). Before the examination, the doctor places drops in her eyes so the doctor can see her retina and determine whether the blood vessels are developing normally. If a baby has any signs of ROP, the doctor will repeat this examination regularly to see if the condition is clearing up on its own, or whether treatment is necessary.

Ultrasound: Ultrasound takes a picture of a baby’s organs using sound waves, rather than x-rays. A small hand-held device called a transducer is rubbed back and forth over the area that the doctor wants to see. An ultrasound examination is painless and done at the baby’s incubator. It often is done to determine if a baby has any bleeding in the brain. A head ultrasound or “head sonogram” is the routine test to diagnose bleeding in the brain.

Urine tests: Like blood tests, urine tests can tell a great deal about a baby’s overall condition. Urine tests can help determine how well the kidneys are functioning, and whether a baby has a urine infection.

Weighing: Every baby is weighed soon after delivery, then at least once a day while he is in the NICU. Don’t be alarmed if your baby loses some weight in the first days or weeks after birth. This is normal, especially for very small babies. When a premature baby starts gaining weight at a steady rate, it is an encouraging sign that he is doing well.

X-rays: X-rays provide pictures of a baby’s lungs, bones and other internal organs. These pictures help the baby’s doctor plan her treatment and monitor her progress. A baby may receive several lung x-rays each day if she has serious breathing problems. She will be exposed to a little radiation from these x-rays. The amount is so low it should not affect her health now or in the future. The baby will not need to be moved to the radiology department for this test; it is done right at her incubator.