Woman's Age No Longer Issue for Down Syndrome Screening

< May. 09, 2007 > -- A new recommendation from the American College of Obstetricians and Gynecologists (ACOG) urges pregnant women to exercise the option to be screened for Down syndrome, regardless of their age.

But ACOG emphasizes that the recommendation should not be automatically applied to all women.

The new recommendation was presented earlier this week at ACOG's annual meeting in San Diego.

"Not every patient wishes to utilize this type of information," says Dr. Deborah Driscoll, chairwoman of the obstetrics-gynecology department at the University of Pennsylvania.

"It's important for patients to understand that this is voluntary," adds Dr. Driscoll, who helped draft the association's recommendations. "Screening isn't right for every patient, and we have to respect the autonomy of patients."

What To Do With Test Information?

Despite technological advances, it is still anything but simple for pregnant women to determine what to do after getting test results that suggest possible problems with a fetus.

At issue is the possibility that an unborn child will develop Down syndrome or other conditions related to chromosome abnormalities. Down syndrome can lead to congenital heart defects and mental retardation.

Genetic testing and counseling have traditionally been offered to women aged 35 and over, because they are at highest risk of giving birth to babies with chromosome problems. An estimated one in 92 mothers in this group gives birth to children with chromosomal disorders.

But the traditional screening tests - amniocentesis or chorionic villus sampling (CVS) - are both considered invasive and pose a small risk to the fetus.

Both tests involve inserting a long needle through a woman's abdomen to obtain fluid or tissue samples for examination in the lab.

The New Recommendation

ACOG now recommends that doctors offer non-invasive screening tests to all mothers before the 20th week of pregnancy. The doctors' group favors a combination of two tests: nuchal translucency (a type of ultrasound exam), and a blood test.

If either of those tests suggests trouble, amniocentesis or chorionic villus sampling may be offered.

"The important take-home message is this: Better testing is available with higher detection rates and lower false-positive rates," says Dr. James D. Goldberg, medical director at San Francisco Perinatal Associates and immediate past chairman of the association's Committee on Genetics.

Mother Should Decide

The ultimate decision about screening, though, should remain with the mother, the doctors say. After all, she must decide whether to continue with a pregnancy if there are indications the child will have a birth defect.

"It's clear that people make a decision on whether to have basic testing based on a number of factors - age, risk, feelings about having a child with a chromosomal abnormality," Dr. Goldberg says. "A lot of things go into individual risk decision-making."

Always consult your physician for more information.

More About Down Syndrome

Down syndrome is a genetic disorder that includes a combination of birth defects, including some degree of mental retardation, characteristic facial features, and, often, heart defects, visual and hearing impairment, and other health problems.

The severity of all of these problems varies greatly among affected individuals. Down syndrome is one of the most common genetic birth defects, affecting approximately one in 800 to 1,000 babies. In the US, there are more than 350,000 individuals with Down syndrome, according to the National Down Syndrome Society.

Life expectancy among adults with Down syndrome is about 55 years, though average lifespan varies. For non-affected adults in the US, life expectancy is approximately 72 to 80 years of age.

The name "Down syndrome" comes from the physician, Dr. Langdon Down, who first described the collection of findings in 1866. It was not until 1959 that the cause of Down syndrome (the presence of an extra #21 chromosome) was identified.

What causes Down syndrome?

Normally in reproduction, the egg cell of the mother and the sperm cell of the father start out with the usual number of 46 chromosomes. The egg and sperm cells undergo cell division where the 46 chromosomes are divided in half and the egg and the sperm cells end up with 23 chromosomes each.

When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby ends up with a complete set of 46 chromosomes, half from the father and half from the mother.

Sometimes, an error occurs when the 46 chromosomes are being divided in half and an egg or sperm cell keeps both copies of the #21 chromosome instead of just one copy. If this egg or sperm is fertilized, the baby ends up with three copies of the #21 chromosome and this is called "trisomy 21" or Down syndrome. The features of Down syndrome result from having an extra copy of chromosome 21 in every cell in the body.

Ninety-five percent of Down syndrome results from trisomy 21.

Always consult your physician for more information.