Overview of Newborn Screening for Birth Defects
State newborn screening is a test performed on every baby born in this country within the first few days of life, to detect serious, life-threatening diseases. State laws require that babies be tested between 2 and 7 days of age, even if the baby seems healthy and has no symptoms of health problems.
How and why is newborn screening performed?
The testing material is usually a few drops of blood taken from the baby's heel and spotted onto a strip of paper called filter paper. The filter paper is sent to a lab for analysis to determine the presence of certain recessive genetic diseases.
Recessive diseases usually occur when healthy parents who unknowingly carry a gene for a recessive disorder, pass the gene to their baby at the same time. The baby inherits two copies of the recessive gene and is affected with the condition.
The specific diseases tested for during the newborn period are often treatable with special diets and/or medications, increasing the baby's chance for a normal life. It is important to detect these diseases as soon as possible to prevent death, mental retardation and other disabilities.
For those conditions where a special diet is required, such as phenylketonuria (PKU) and galactosemia, a pediatric metabolic specialist and nutritionist are needed to educate parents about appropriate foods.
Parents also need to be educated about monitoring the levels of certain compounds in blood and urine to ensure the infant is not harmed by the disease.
What diseases are newborns screened for?
The diseases screened for depends on where you live. In most states, testing is done for phenylketonuria (PKU), hypothyroidism, galactosemia, sickle cell disease and other hemoglobin disorders.
PKU is a recessive disorder, which occurs in about one in 10,000 to 25,000 live births. PKU is caused by the absence of the enzyme phenylalanine hydroxylase. This enzyme normally converts phenylalanine (present in dietary protein) to tyrosine.
Infants with PKU may be asymptomatic for many weeks. However, when PKU infants begin to eat foods containing phenylalanine, they can have delays in development, including small head size, mental retardation, seizures, hyperactivity and a decreased growth rate.
Dietary restriction of phenylalanine is needed to treat PKU. These dietary restricitions should begin immediately after birth, continuing throughout life. If left untreated, most persons with PKU have an IQ less than 50.
Congenital hypothyroidism, a condition causing inadequate production of the thyroid hormone, is seen in one out of every 4,000 live births. The cause is usually total or partial failure of the thyroid gland to develop, or its development is in an abnormal location.
Infants with hypothyroidism can appear healthy for the first several months of life. Clinical signs can develop, including jaundice, constipation, poor muscle tone, feeding problems, lethargy, swollen face, large tongue, umbilical hernia and hypothermia.
If left untreated severe mental retardation, growth delays, deafness and other neurological abnormalities can occur. To treat congenital hypothyroidism, synthetic thyroid hormone is given daily in most cases. The thyroid gland is evaluated periodically by blood tests and evaluations of the baby's growth and development.
Galactosemia is a recessive disorder, which occurs in one out of every 60,000 to 80,000 live births. Galactosemia is caused by a deficiency of one of three enzymes responsible for metabolizing galactose.
Galactose is a component of lactose, found in human and other animal milk. Infants with galactosemia may be asymptomatic for many months. After a few days to a few weeks after milk feeding is initiated, the symptoms often begin to develop. They include vomiting, diarrhea, lethargy, failure to thrive, jaundice, cataracts (depending on the enzyme deficiency), hypoglycemia and sepsis (infection).
Without rapid diagnosis and treatment, death can result. If the infant survives the neonatal period but continues untreated, progressive mental retardation, growth failure, cataracts, enlarged liver and motor retardation may result.
Dietary restriction of galactose and lactose is needed to treat galactosemia and should begin as soon as possible after birth and continued throughout the life of an individual with galactosemia.
Sickle cell disease
Sickle cell disease is one of the most common, inherited single gene disorders among Black/African-Americans. About one out of every 500 Black/African-American babies are born with sickle cell disease. One out of every 12 Black/African-American people carries the gene for sickle cell disease.
Sickle cell disease involves the red blood cells, or hemoglobin, and their ability to carry oxygen. Normal hemoglobin cells are smooth, round, and flexible, like the letter O. This helps blood cells move through the vessels in our bodies easily. Sickle cell hemoglobin cells are stiff and sticky, forming into the shape of a sickle.
These sickle cells tend to cluster together and cannot easily move through the blood vessels. The cluster causes a blockage, stopping the movement of healthy, normal oxygen carrying blood. This blockage is what causes the painful and damaging complications of sickle cell disease.
Sickle cells only live for about 15 days, whereas normal hemoglobin cells can live up to 120 days. Also, sickle cells risk being destroyed by the spleen because of their shape and stiffness.
The spleen is an organ that helps filter the blood of infections. Sickled cells get stuck in this filter and die. Due to the decreased number of hemoglobin cells circulating in the body, a person with sickle cell is chronically anemic. The spleen also suffers damage from the sickled cells blocking healthy oxygen carrying cells.
After repeated blockages, the spleen is very small and does not work properly. Without a functioning spleen, these individuals are more at risk for infections. Infants and young children are at risk for life-threatening infections. Treatment includes prompt emergency care for fevers and infections, appropriate vaccinations, penicillin and management of anemia.