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Prenatal screening vs newborn screening. (ask the doctor).

Q What is the difference between prenatal screening and newborn screening? How do I know when I need one, the other, or both? Why is screening so important?

A Both prenatal screening and newborn screening have a similar goal: to identify whether the baby has any health problems. Parents can certainly benefit from both prenatal and newborn screening, as each provides different types of information about a baby's health. The most significant difference between the two types of testing is actually a matter of timing. Prenatal testing is performed on the mother during pregnancy; newborn screening is performed after the baby is born.


Prenatal tests that you may have heard of include ultrasound, amniocentesis and maternal blood tests. This form of testing also tends to be a more targeted form of testing. In other words, the types of tests performed are based on the mother's age and medical history, family history of certain medical conditions, or other concerns specific to each baby or each pregnancy. As a matter of fact, screening and genetic counseling may also be offered to a couple before conception, under certain circumstances. Speak with your obstetrician to learn more about prenatal testing and the types of tests he or she recommends for you and your baby.


Newborn screening is a more general type of testing that is performed the same way on every baby and is not targeted to specific issues or concerns. The actual procedure is quite simple. A small sample of blood is obtained by pricking a baby's heel, usually on the second day of life. The blood then dries on absorbent paper and is sent to a laboratory for analysis using sophisticated technology, such as tandem mass spectrometry. At my hospital, abnormal results are provided to both the hospital and the baby's pediatrician within 24 to 48 hours of birth. Newborn screening also offers a simple, inexpensive way of determining whether a baby has a metabolic disorder that, if left untreated, could result in permanent neurological or developmental damage, even death. Metabolic disorders, which affect at least 1 in 1,000 babies born in the United States each year, are inherited genetic disorders that interfere with the body's ability to break down fats, sugars, or proteins in food.

Most babies born with these disorders look and act perfectly healthy at first. Without newborn screening, the problem is not discovered until the child develops symptoms, which is often too late to prevent permanent damage. While these diseases cannot be completely cured, they can usually be treated, reducing--and in some cases eliminating-the risks to the child. Treatment is often as simple as monitoring or removing the food that cannot be metabolized from the child's diet.

One of the more common of the metabolic disorders, and one for which all babies are now routinely tested, is phenyletonuria (PKU), characterized by the inability to process the amino acid phenylalinine, which is commonly found in protein-rich foods. Another is MCAD (medium chain acyl-CoA dehydrogenase deficiency), a disorder that affects the ability to process fat and may be responsible for up to 10 percent of deaths attributed to sudden infant death syndrome.

Others are maple syrup urine disease, a disorder in which several amino acids can not be metabolized properly; cystic fibrosis, the most common inherited metabolic disease among Caucasians; galactosemia, an inability to properly digest galactose, a type of sugar found in milk; and glutaric acidemia (Type I), a disorder of amino acid metabolism characterized by the build-up of glutaric acid.


But early identification is the key. I am an avid supporter of newborn screening, particularly universal newborn screening, meaning all newborns should receive all available tests. Unfortunately, the rules in each state vary widely and currently many babies receive only very limited testing. (see EP Magazine, August, 2002 for a listing by state).

In fact, many states mandate evaluation for only four to six disorders. Some states, including New Jersey, where I live and practice, have adopted expanded newborn screening, For example, New Jersey recently expanded its list of mandatory tests from 4 to 14 metabolic disorders. I do not think that goes far enough. Right now, technology is available to test for more than 50 potentially treatable metabolic disorders. At The Valley Hospital in Ridgewood, we recently made the decision to contract with a private laboratory to test every single baby born at the hospital for these more than 50 disorders.

We also offer universal hearing tests. In most cases, the tests serve to reassure parents that their baby is healthy. And in those cases in which problems are discovered, parents can also take comfort in knowing that appropriate treatment was initiated days after birth, giving their baby the best possible start in life.

The good news is that efforts are underway to close the wide disparity in newborn screening guidelines among the states. And I am hopeful that universal newborn screening will become a reality in the not-so-distant future. But in the meantime, I urge you and other expectant parents to take matters into your own hands. You are, after all, your baby's best advocate.

First, find out what screening tests your local hospital routinely performs. If you are lucky, you will find a hospital in your area that offers screening for the full range of metabolic disorders. If not, talk to your obstetrician and pediatrician--they may be able to assist in making arrangements with a private lab for expanded screening. Or you can call a private lab directly to make arrangements to have your baby screened.

Ask the Doctor addresses issues of concern to our readers. Parents should review any suggestions made in this column with the appropriate professionals. Mention of specific products or medications illustrate suggestions and are not endorsements of any specific products. Send questions to: Ask the Doctor, EXCEPTIONAL PARENT, 65 East Route 4, River Edge, NJ 07661; Fax: (201) 489-0074; or E-mail:

Frank Manginello, M.D.

Director of Neonatology and Medical Director, Center for Child Development, The Valley Hospital, Ridgewood, NJ.
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Author:Manginello, Frank
Publication:The Exceptional Parent
Geographic Code:1USA
Date:Oct 1, 2002
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