Vital Newborn Screening Tests

Tests given to newborns are vital to lifelong health.

The Purpose of Newborn Screening

Sometime during first few days of life, a doctor or nurse will prick baby's heel to test his blood. For the very rare child who can't break down fats, sugars, or proteins because of a metabolic disorder -- a problem with the body's chemistry -- newborn blood screening tests can prevent serious complications and even death.

Newborn screening tests aim to detect treatable metabolic disorders. Most states today screen for three to eight disorders. They use a relatively new technique in which two instruments called spectrometers sort and weigh the molecules in the blood sample. By studying these measurements, scientists can detect abnormalities and diagnose metabolic disorders before a child falls ill.

For a disorder to be screened:

  • It must be treatable.
  • There must be an accurate, cost-effective test.
  • Early medical intervention must be able to help the infant.

Tests to Expect

Your doctor or your state's department of health can tell you which tests will be given to your baby. These are the diseases usually tested for:

  • Congenital hypothyroidism: This problem is caused when a baby's body doesn't make enough thyroid hormone, which can lead to poor growth and mental retardation. Early treatment with thyroid medication can help the child grow and develop normally.
  • Phenylketonuria (PKU): This prevents a baby's body from breaking down the amino acid phenylalanine, found in the protein of foods. A buildup of this substance can damage a baby's brain and cause mental retardation. If the baby is started on a special low-phenylalanine diet early, mental retardation can be prevented.
  • Hemoglobin disorders (such as sickle cell disease): These are caused by abnormal red blood cells that do not transport oxygen efficiently. The blood cells may become deformed, causing anemia and clogged blood vessels. A baby with this disorder is also likely to have pain, strokes, and life-threatening infections. Treatment with antibiotics may prevent serious infections in early childhood.
  • Biotinidase deficiency: This is caused by an enzyme deficiency that can lead to seizures, developmental delay, eczema, and hearing loss. Problems can be prevented with biotin treatment when the condition is detected early.
  • Galactosemia: This occurs when a baby can't break down the sugar that occurs in milk. In some cases, life-threatening damage to the brain and liver can occur as early as one week after birth. When started early, a special milk-free diet prevents these problems.
  • Maple syrup urine disease (MSUD): This is caused by not being able to break down certain proteins properly. It can result in mental retardation, seizures, or death. The name of the disorder comes from the distinctive maple syrup odor of the urine. When detected early, infants are put on a special diet to avoid severe effects.
  • Homocystinuria: This is caused when certain parts of the protein homocystine can't be broken down. It can lead to mental retardation, eye problems, and blood clots. With early detection, infants are put on a low methionine diet with cystine supplementation to avoid these problems.
  • Congenital adrenal hyperplasia: This is caused by a deficiency of certain hormones that affect genital development. Serious loss of body salt and water, even death, may occur. Medications and treatments are available to correct the condition.

Other Detectable Disorders

Blood tests aren't the only important kind of screening for newborns. Every baby should have a thorough physical examination in his first 24 hours to screen for problems such as heart murmurs, hearing problems, developmental hip dislocations, rare tumors such as retinoblastoma, and many others that are important to discover early.

Some states also test for:

  • Tyrosinemia
  • Toxoplasmosis
  • Medium-chain acyl-CoA dehydrogenase (MCAD)
  • Cystic fibrosis
  • Human immunodeficiency virus (HIV)
  • Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Additional Facts About Screening

According to the March of Dimes:

  • Screening tests should be done 24 to 48 hours after birth.
  • Testing all babies is important, because most babies appear healthy at first, even the babies with these disorders.
  • Parents who have no family history of problems or who have already had healthy children can still have children with one of these diseases.
  • In fact, most children who are affected come from families with no previous history of the condition.
  • If one of your children has a disorder, your other children should be tested, but will not necessarily have the disease.
  • In most states you may refuse to take the tests for religious or personal reasons. If you do, you may be asked to sign a refusal form. This form relieves your doctor of liability for damages that result from a disorder that could have been detected by screening.
  • Sometimes a baby needs to be retested because the sample was flawed (for example, not enough blood was in the sample or it was taken at the wrong time).
  • Premature or low birth weight newborns are more likely to have abnormal test results on the first specimen even if a disorder is not present.
  • If test results show that further evaluation is needed, your baby's doctor will be called right away.

Reviewed 11/02 by Elizabeth Stein, CNM

All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.

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