New prenatal test questioned

September 19, 2008 12:01:22 PM PDT
Ask any expectant parent what they hope for most and you'll probably hear "a healthy baby." But deciding if or how you want to check up on a developing fetus can be very nerve wracking. A newer kind of screening procedure is easing those fears.

You've probably heard of amniocentesis. They're tests to determine if a fetus has any birth defects, including Down syndrome. They're accurate, but they carry the small risk of miscarriage.

Enter a newer, non-invasive procedure that's generating a lot of excitement. But some doctors are starting to question whether this early screen is leaving expectant parents with a false sense of security.

For an expectant parent, the first sound of a baby's heartbeat is not only thrilling, it's comforting. But listening in on the fetus offers little insight into what's really going on.

Thirty-six-year-old Tammy Lee wanted to know more but worried about the possible risks of miscarriage with invasive testing. So she opted instead for first trimester combined screening. It begins with something called nuchal translucency screening. Lee had the test at Female Healthcare Associates in Bloomingdale.

"It's becoming very popular I think with non invasive part of the procedure and lower false positives people are thinking this is a pretty good," said Dr. Steven Binette, OBGYN, Female Healthcare Associates.

A very detailed ultrasound is performed and the back of the fetus' neck is measured because there is a strong association between the thickening of the neck and the risk of Down syndrome. This has to be done early in the pregnancy, between 11 and 13 weeks. This measurement is combined with the results of blood tests to determine risk of Down syndrome.

"Most of the studies suggest that the detection is near 80-90 percent with a lower false positive than the blood tests," Binette said.

The noninvasive screening is generating a lot of buzz because it's seen as an accurate and safer way to look for birth defects. The results won't produce a diagnosis, but they can assess the baby's risk for certain problems. .

"The NT scan is a screening test, and it only tells you that they are at increased risk of having a problem. It doesn't tell you if you are having a problem," Binette.

And that could be causing some confusion. Some overzealous doctors are touting this as comparable to amniocentesis.

"It's definitely being oversold," said Dr. Lee Shulman, the head of reproductive genetics at Northwestern Memorial Hospital. Shulman worries some women may think they are getting a definitive answer. Amnio involves the actual extraction of genetic material and is nearly 100 percent accurate at determining genetic problems.

"It's not that people are trying to con you into doing this screening test. You need to understand the difference in screening and diagnosis. Understand the information you are going to get from each test," Shulman said.

Lee is pregnant with her second child. She said she understands the early screening will not give her a definite answer but she's comfortable with the information it can provide. Results show she is not at high risk.

"I felt reassured that they would know exactly what was going on," Lee said.

Women who go with screening and learn their baby is at risk of a birth defect may ultimately decide to go with the more invasive tests. More women will likely be offered screening for Down syndrome now that the American College of Obstetricians and Gynecologists is recommending screening for all pregnant women regardless of their age.

Dr. Steven P. Binette
Female Healthcare Associates
471 Army Trail Rd.
Suite 101
Bloomingdale, Il.
630-980-3366

Dr. Lee P. Shulman
Ob-Gyn, Chief, Division of Reproductive Genetics
Northwestern Memorial Hospital
250 E. Superior
Chicago, Il
60611
312-926-2000

American College of Obstetricians and Gynecologists
acog.org

MedlinePlus: Prenatal Testing
nlm.nih.gov


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