Definition

Newborn screening tests look for developmental, genetic, and metabolic disorders in the newborn baby. This allows steps to be taken before symptoms develop. Most of these illnesses are very rare, but can be treated if caught early.

The types of newborn screening tests that are done vary from state to state. By April 2011, all states reported screening for at least 26 disorders on an expanded and standardized uniform panel. The most thorough screening panel checks for about 40 disorders. However, because phenylketonuria (PKU) was the first disorder for which a screening test developed, some people still call the newborn screen "the PKU test".

In addition to blood tests, screening for hearing loss and critical congenital heart disease (CCHD) is recommended for all newborns. Many states require this screening by law as well.

Alternative Names

Infant screening tests; Neonatal screening tests; The PKU test

How the Test is Performed

Screenings are done using the following methods:

• Blood tests. A few drops of blood are taken from the baby's heel. The blood is sent to a lab for analysis.
• Hearing test. A health care provider will place a tiny earpiece or microphone in the infant's ear. Another method uses electrodes that are put on the baby's head while the baby is quiet or asleep.
• CCHD screen. A provider will place a small soft sensor on the baby's skin and attach it to a machine called an oximeter for a few minutes. The oximeter will measure the baby's oxygen levels in the hand and foot.

How to Prepare for the Test

There is no preparation needed for newborn screening tests. The tests are most often done before leaving the hospital when the baby is between 24 hours and 7 days old.

How the Test will Feel

The baby will most likely cry when the heel is pricked to get the blood sample. Studies have shown that babies whose mothers hold them skin-to-skin or breastfeed them during the procedure show less distress. Wrapping the baby tightly in a blanket, or offering a pacifier dipped in sugar water, may also help ease pain and calm the baby.

The hearing test and the CCHD screen should not cause the baby to feel pain, cry, or respond.

Why the Test is Performed

Screening tests do not diagnose illnesses. They show which babies need more testing to confirm or rule out illnesses.

If follow-up testing confirms that the child has a disease, treatment can be started, before symptoms appear.

Blood screening tests are used to detect a number of disorders. Some of these may include:

• Amino acid metabolism disorders
• Biotinidase deficiency
• Congenital adrenal hyperplasia
• Congenital hypothyroidism
• Cystic fibrosis
• Fatty acid metabolism disorders
• Galactosemia
• Glucose-6-phosphate dehydrogenase deficiency (G6PD)
• Human immunodeficiency disease (HIV)
• Organic acid metabolism disorders
• Phenylketonuria (PKU)
• Sickle cell disease and other hemoglobin disorders and traits
• Toxoplasmosis

Normal Results

Normal values for each screening test may vary depending on how the test is performed.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means that the child should have additional testing to confirm or rule out the condition.

Risks

Risks for the newborn heel prick blood sample include:

• Pain
• Possible bruising at the site where the blood was obtained

Considerations

Newborn testing is critical for the baby to receive treatment. Treatment may be lifesaving. However, not all disorders that can be detected can be treated.

Although hospitals do not perform all screening tests, parents can have other tests done at large medical centers. Private labs also offer newborn screening. Parents can find out about extra newborn screening tests from their provider or the hospital where the baby is born. Groups like the March of Dimes -- www.marchofdimes.org also offer screening test resources.

References

Centers for Disease Control and Prevention website. About newborn screening. www.cdc.gov/newborn-screening/about/index.html. Updated May 13, 2024. Accessed June 19, 2024.

McCandless SE, Kripps KA. Genetics, inborn errors of metabolism, and newborn screening. In: Fanaroff AA, Fanaroff JM, eds. Klaus and Fanaroff's Care of the High-Risk Neonate. 7th ed. St Louis, MO: Elsevier; 2020:chap 6.

Sahai I. Newborn screening. In: Gleason CA, Sawyer T, eds. Avery's Diseases of the Newborn. 11th ed. Philadelphia, PA: Elsevier; 2024:chap 18.