Newborn screening in the United States tests for up to 38 core conditions, plus hearing loss and heart defects, using a combination of a blood sample, a hearing check, and a pulse oximetry reading. Most of these conditions are rare but treatable, and catching them in the first days of life can prevent serious disability or death.
Three Parts of Newborn Screening
Newborn screening isn’t a single test. It has three distinct parts, each looking for different types of problems.
The blood spot test (sometimes called the heel prick) is the part most parents remember. A few drops of blood are collected from your baby’s heel, applied to a special card, and sent to a state laboratory. That single blood sample is analyzed for dozens of metabolic, hormonal, and genetic conditions. The second part is a hearing screening, done with tiny earbuds or sensors placed on your baby’s head, which checks whether the ears and brain are responding to soft sounds. The third is pulse oximetry, where a small sensor wrapped around your baby’s hand and foot measures oxygen levels in the blood to flag possible heart defects.
Metabolic Conditions
The largest group of conditions on the screening panel involves the body’s ability to break down food into energy. These are called metabolic disorders, and most are caused by a missing or malfunctioning enzyme. Without early treatment, toxic substances can build up in the blood and damage the brain, organs, or muscles. With early treatment, many children with these conditions live healthy lives.
The most well-known is phenylketonuria, or PKU. Babies with PKU can’t break down an amino acid called phenylalanine, which is found in most protein-containing foods. The blood spot test measures phenylalanine levels directly. Left untreated, it causes intellectual disability; caught early, it’s managed with a modified diet.
Other metabolic conditions on the panel include maple syrup urine disease (named for the distinctive smell it gives urine), several forms of methylmalonic acidemia, propionic acidemia, and classic galactosemia, where a baby can’t process the sugar in milk. There are also a group of fatty acid oxidation disorders, the most common being medium-chain acyl-CoA dehydrogenase deficiency, or MCADD. Babies with MCADD can’t properly convert certain fats to energy, which can cause dangerous drops in blood sugar during illness or fasting. In total, metabolic conditions make up the majority of the 38 core conditions on the federal panel.
Hormone-Related Conditions
Two endocrine conditions are on the panel. Primary congenital hypothyroidism means a baby’s thyroid gland doesn’t produce enough hormone for normal growth and brain development. It’s one of the more common conditions caught by screening, affecting roughly 1 in 2,000 to 4,000 newborns. Treatment is a daily thyroid hormone replacement, and outcomes are excellent when it starts early.
Congenital adrenal hyperplasia affects the adrenal glands, which produce cortisol and other hormones. Without treatment, it can cause life-threatening salt-wasting crises in the first weeks of life, particularly in boys where the condition is less physically obvious at birth.
Blood Disorders
The screening panel includes three forms of sickle cell disease: sickle cell anemia (HbSS), sickle-hemoglobin C disease, and sickle beta-thalassemia. Laboratories identify these by separating the different types of hemoglobin in the blood sample using techniques like high-performance liquid chromatography or capillary electrophoresis. These methods can also detect other hemoglobin variants beyond the three specifically listed on the panel. Babies identified with sickle cell disease are started on preventive antibiotics, which dramatically reduces the risk of fatal infections in infancy.
Cystic Fibrosis and Immune Deficiencies
Cystic fibrosis, which causes thick mucus buildup in the lungs and digestive system, is detected through the blood spot. Early identification allows treatment to begin before significant lung damage occurs. Severe combined immunodeficiency, sometimes called “bubble boy disease,” is also on the panel. Babies with this condition are born with virtually no functioning immune system and are extremely vulnerable to infections. Screening catches it early enough for a bone marrow transplant or gene therapy to be effective.
Spinal muscular atrophy, a genetic condition that destroys the nerve cells controlling muscle movement, was added to the panel in 2018. Newer therapies can slow or halt the disease, but they work best when given before symptoms appear, making newborn screening critical.
Hearing and Heart Screening
Hearing loss affects about 1 to 3 of every 1,000 babies born in the U.S. The screening uses one of two methods. In the first, small earbuds play soft sounds and a computer measures whether the inner ear produces a response. In the second, earphones play sounds while sensors on the baby’s head and neck measure how the brain processes them. Both are painless and usually done while the baby sleeps. A baby who doesn’t pass is referred for more detailed testing; not passing the initial screen doesn’t necessarily mean the baby is deaf or hard of hearing.
Critical congenital heart disease screening uses pulse oximetry, a painless sensor placed on the baby’s right hand and one foot. It measures how much oxygen is in the blood. Certain heart defects cause oxygen levels to be lower than normal, and this simple test can catch problems that aren’t visible on a physical exam. It’s typically done at least 24 hours after birth.
Recent Additions to the Panel
The federal screening panel has expanded significantly over the past decade. Pompe disease, a condition where a buildup of complex sugars damages the heart and muscles, and X-linked adrenoleukodystrophy, which affects the brain’s protective nerve coating, are both relatively recent additions. Mucopolysaccharidosis types I and II, which involve the buildup of complex sugars throughout the body, were added as enzyme replacement therapies became available.
Guanidinoacetate methyltransferase deficiency, or GAMT deficiency, which affects brain development and can cause seizures and intellectual disability, was added as a core condition. The most recent addition, accepted by the Secretary of Health and Human Services in December 2025, is metachromatic leukodystrophy (MLD), a rare genetic condition that leads to progressive damage to the brain and motor function.
What Your State Actually Screens For
The 38 core conditions, plus 26 secondary conditions that may be identified incidentally during testing, form the Recommended Uniform Screening Panel maintained by the Department of Health and Human Services. This is a federal recommendation, not a mandate. Newborn screening is a state-run program, and each state decides which conditions to include. Most states screen for all or nearly all of the core conditions, but some lag behind, particularly for the most recently added ones. You can check your state’s specific panel through the HRSA website at newbornscreening.hrsa.gov.
The 26 secondary conditions are disorders that labs may detect while testing for the core conditions. They aren’t the primary target of screening, but if the lab spots them, they’re reported. These include milder variants of conditions on the core list, like benign hyperphenylalaninemia (a less severe form of PKU) and several additional fatty acid and organic acid disorders.
Understanding Your Baby’s Results
Most families receive normal results and never think about newborn screening again. An abnormal or “out of range” result does not mean your baby has a condition. It means more testing is needed. False positives are common, especially in premature or low-birth-weight babies. One hospital study found that over 20% of premature infants had at least one false positive result on their initial screen, with rates even higher among the smallest babies. Follow-up testing, which may include a repeat blood spot, additional blood work, or genetic testing, typically clarifies the result. A true positive on newborn screening leads to a referral to a specialist, and for most conditions on the panel, treatment can begin within the first weeks of life.