What are newborn screening tests?

Nearly all babies will have a simple blood test to check for disorders that are not apparent immediately after delivery. Some of these disorders are genetic, metabolic, blood, or hormone-related. Each state in the United States requires screening tests, but the specific tests performed vary among the states.

A heel-prick is used to sample the baby's blood. The blood drops are collected in a small vial or on a special paper. The blood is then sent for testing. The baby's heel may have some redness at the pricked site, and some babies may have bruising, but this usually disappears in a few days.

Newborn screening tests may include:

• Phenylketonuria (PKU). PKU is an inherited disease in which the body cannot metabolize a protein called phenylalanine. It is estimated that one in every 10,000 to 15,000 babies is born with PKU in the U.S. Without treatment, PKU can cause intellectual disability. Newborn screening for PKU is required in all 50 states.
• Congenital hypothyroidism. This is a condition in which the baby is born with too little thyroid hormone. Hypothyroidism is also quite common and has almost doubled in the past 20 years to approximately one in 2,500 to 3,000 babies born in the U.S. Untreated low thyroid hormone levels can lead to mental developmental problems and poor growth. All 50 states screen for hypothyroidism.
• Galactosemia. This is an inherited disorder in which the baby is unable to metabolize galactose, a milk sugar. It is estimated to occur in about one baby in every 53,000 births. Without treatment (avoidance of milk), galactosemia can be life threatening. Symptoms may begin in the first two weeks of life. All states screen for galactosemia.
• Sickle cell disease. This inherited disorder occurs primarily in African Americans, but may also occur in Hispanics and Native Americans. The disease causes a severe form of anemia. There are different types of the disease. The disease occurs in about one out of every 365 African American births and one out of every 16,300 Hispanic American births. Early diagnosis of sickle cell disease can help lower some of the risks which include severe infections, blood clots, and stroke.
• Maple syrup urine disease. This is an inherited disorder that is very common in the Mennonite population. The disorder is caused by an inability of the body to properly process certain parts of protein called amino acids. The name comes from the characteristic odor of maple syrup in the baby's urine caused by the abnormal protein metabolism. If untreated, it is life threatening as early as the first two weeks of life. Even with treatment, severe disability and paralysis can occur.
• Homocystinuria. This inherited disorder affects one in 200,000 babies and causes intellectual disability, bone disease, and blood clots. It is caused by a deficiency of an enzyme necessary to digest an amino acid called methionine.
• Biotinidase deficiency. This inherited disorder is characterized by a deficiency of the biotinidase enzyme. This enzyme is important in metabolizing biotin, a B vitamin. It affects one in 60,000 to 75,000 babies in the U.S. and is most common in the people of European descent. Lack of the enzyme can lead to severe acid build up in the blood, organs, and body systems.
• Congenital adrenal hyperplasia. Most states screen for this inherited disease of the adrenal glands. Babies born with congenital adrenal hyperplasia (CAH) cannot make enough of the hormone cortisol, which helps control energy, sugar levels, blood pressure, and how the body responds to the stress of injury or illness. The Endocrine Society estimates the incidence of CAH at one in about 15,000, depending on the severity of the disease. It is extremely common in a certain group of Eskimos in western Alaska. CAH may also affect the development of the genitals and the hormones of puberty.
• Medium chain acyl-CoA dehydrogenase deficiency (MCAD). This disorder of fatty acid oxidation can cause sudden death in infancy and serious disabilities in survivors, such as intellectual disability. MCAD affects about one baby per 15,000 births, almost exclusively in people of northwestern European descent.

Other tests screen for disorders including cystic fibrosis, amino acid disorders, fatty acid oxidation disorders, hemoglobin disorders, lysosomal storage disorders, organic acid disorders, and severe combined immunodeficiency.

Most screenings cannot be performed until a baby has received at least 24 hours of breast milk or formula. Your baby may need follow-up testing if you are discharged before this time or the baby is unable to be tested before discharge. 

Most states screen for hearing loss and critical congenital heart defects.

• Hearing loss. Three in every 1,000 newborns have significant hearing loss, and nearly all states screen newborns for hearing loss.
• Critical congenital heart disease (CCHD) is estimated to affect two out of every 1,000 babies born each year in the US. Pulse oximetry is a non-invasive test that measures how much oxygen is in the blood and can help to identify babies that may be affected with CCHD before they leave the newborn nursery.