Newborn Screening Tests

doctor and baby

Which Tests Are Offered?

Newborn screening varies by state and is subject to change, especially given advancements in technology. However, the disorders listed here are those usually included in newborn screening programs:

1) phenylketonuria (PKU)

Phenylketonuria (PKU) is a metabolic disorder. Metabolism is the process in the body that converts the fuel from food into energy needed to do everything from moving to thinking to growing. A metabolic disorder is any disease caused by an abnormal chemical reaction in the body's cells.

Babies with PKU are missing an enzyme that's needed to process phenylalanine. Phenylalanine is an amino acid necessary for normal growth in kids and for normal protein use. Amino acids are the "building blocks" for the proteins that make up our muscles and other important parts of our bodies. 

If too much phenylalanine builds up, it damages brain tissue and cause developmental delay.

When PKU is detected early, feeding an infant a special formula low in phenylalanine can prevent intellectual disability. A low-phenylalanine diet is needed throughout childhood and adolescence and sometimes into adult life. This diet cuts out all high-protein foods, so people with PKU often need to take a special artificial formula as a nutritional substitute. 

2) Congenital hypothyroidism

previously known as cretinism, is a severe deficiency of thyroid hormone in newborns. It causes impaired neurological function, stunted growth, and physical deformities. The condition may occur because of a problem with the baby’s thyroid gland, or a lack of iodine in the mother’s body during pregnancy.

A baby’s body needs iodine to make thyroid hormones. These hormones are essential for healthy growth, brain, and nervous system development.


Signs of cretinism or congenital hypothyroidism in a newborn include:

  • lack of weight gain
  • stunted growth
  • fatigue, lethargy
  • poor feeding
  • thickened facial features
  • abnormal bone growth
  • mental retardation
  • very little crying
  • excessive sleep
  • constipation
  • yellowing of the skin and whites of the eyes
  • floppiness, low muscle tone
  • hoarse voice
  • unusually large tongue
  • swelling near the navel
  • cool, dry skin
  • pale skin
  • swelling of the skin (myxedema)
  • swelling in the neck from an enlarged thyroid gland (goiter)

3) Galactosemia

Galactosemia is a disorder that affects how the body processes a simple sugar called galactose. A small amount of galactose is present in many foods. It is primarily part of a larger sugar called lactose, which is found in all dairy products and many baby formulas. The signs and symptoms of galactosemia result from an inability to use galactose to produce energy.

Classic galactosemia, also known as type I, is the most common and most severe form of the condition

If infants with classic galactosemia are not treated promptly with a low-galactose diet, life-threatening complications appear within a few days after birth. Affected infants typically develop feeding difficulties, a lack of energy (lethargy), a failure to gain weight and grow as expected (failure to thrive), yellowing of the skin and whites of the eyes (jaundice), liver damage, and abnormal bleeding. Other serious complications of this condition can include overwhelming bacterial infections and shock.

4) G6PD Deficiency

G6PD deficiency is a genetic disorder that most often affects males. It happens when the body doesn't have enough of an enzyme called glucose-6-phosphate dehydrogenase (G6PD).

G6PD helps red blood cells work. It also protects them from substances in the blood that could harm them.

In people with G6PD deficiency, either the red blood cells do not make enough G6PD or what they do make doesn't work as it should. Without enough G6PD to protect them, the red blood cells break apart. This is called hemolysis. When many red blood cells are destroyed, a person can develop hemolytic  anemia. This can cause tiredness, dizziness, and other symptoms.


Maple syrup urine disease is an inherited disorder in which the body is unable to process certain protein building blocks (amino acids) properly. The condition gets its name from the distinctive sweet odor of affected infants' urine. It is also characterized by poor feeding, vomiting, lack of energy (lethargy), abnormal movements, and delayed development. If untreated, maple syrup urine disease can lead to seizures, coma, and death.

Maple syrup urine disease is often classified by its pattern of signs and symptoms. The most common and severe form of the disease is the classic type, which becomes apparent soon after birth. Variant forms of the disorder become apparent later in infancy or childhood and are typically milder, but they still lead to delayed development and other health problems if not treated.

How Screening Is Done?

In the first 2 or 5 days of life, your baby's heel will be pricked to get a small blood sample for testing.