Posted On: December 14, 2012 by Patrick A. Malone

New Prenatal Test Is Less Risky but Less Trustworthy

Prospective parents who want to know if their baby has a genetic disorder such as Down syndrome are advised to consider amniocentesis or chorionic villus sampling (CVS). Amnio, generally performed during the second trimester, involves inserting a needle into the amniotic fluid surrounding the fetus. The CVS probe removes a sample of the sac surrounding the fetus toward the end of the first trimester. Both carry a small risk of miscarriage.

So some people are choosing a different procedure that can be done as early as 10 weeks into the pregnancy and involves only drawing the mother’s blood. Three versions of the test have been available for a year, and although its convenience is appealing, according to a recent story by Kaiser Health News and the Washington Post, the decision to use it is complicated. The technology is not subject to regulation by the FDA, and the body of research about its accuracy is slim.

Thousands of the tests have been performed (at a cost of as much as $1,900) while they remain under review. Insurance companies don’t (yet) cover the cost, and because the test is so new, it’s unclear if, eventually, it will reduce miscarriages and the cost of complications by reducing the use of the more invasive tests. Will the tests, instead, increase costs because women who otherwise would pass on amniocentesis will opt for the blood draw?

According to the KHN/Post story, amnio is performed about 200,000 times every year in the U.S. In the Washington, D.C. area it costs about $2,500. As a standard test, it’s generally included in maternity coverage.

The new tests, typically, are offered only to women whose age and medical history put their fetus at a higher risk of having a chromosome abnormality; standard screening tests often are offered to all pregnant women.

The risks of having a fetus with a genetic disorder are greater if the mother:

  • is 35 or older;

  • has a history of miscarriages or children born with birth defects;

  • has a family history of genetic disease.

In addition, prenatal genetic testing is recommended if either parent has a family history of genetic disease or is known to be a carrier of a genetic disease.

The new test examines DNA fragments to see if a fetus carries three instead of the normal two copies of chromosomes 21, 18 or 13. An extra copy of 21, a called trisomy 21, is the main cause of Down syndrome; and extra copy of 18, called trisomy 18, causes a less common disorder, Edwards syndrome. Trisomy 13 is also known as Patau syndrome. All three are linked to serious developmental and medical problems.

Earlier this year, we wrote about the fate of babies handicapped by two of these conditions.

The test checks the mother’s blood levels of pregnancy-associated proteins and hormones and includes an ultrasound to see if there’s extra fluid at the back of the fetus' neck. The two procedures appear to detect about 9 in 10 cases of Down syndrome, and an even higher ratio of trisomies 18 and 13.

As the KHN/Post story says, 5 in 100 tests result in a false-positive—that is, showing a defective gene when there isn’t one. Only amniocentesis or CVS provide definitive answers.

Last month the American College of Obstetricians and Gynecologists said that the tests "should not be part of routine prenatal laboratory assessment." The organization hedged that statement, however, by noting that the tests can be offered to patients at increased risk of having a baby with a trisomy, but must be preceded by counseling about their limitations. Other professional groups, the National Society of Genetic Counselors and the International Society for Prenatal Diagnosis, agreed.

Given the lack of research proving the accuracy of the new test, all three organizations recommend that anybody who received a positive result undergo amniocentesis or chorionic villus sampling to verify the diagnosis.

So the question arises: If you have to confirm a diagnosis, should you have the test in the first place? Is the minimal risk of complication, in comparison to the greater, but still small risk of miscarriage with the standard, proven tests, worth it?

Maybe, especially if you are in the high-risk group for fetal genetic abnormalities. And although cost might be a factor, at this point, the companies who market the tests offer considerable subsidies. According the KHN/Post story, “[T]he most that women with insurance have to pay out of pocket is $235 for the MaterniT21 Plus test (list price $1,900) and $200 for Verifi (list price $1,200), even if their plan declines to cover the test. Both companies offer self-pay options for women without insurance: The price is $450 to $500 for MaterniT21 Plus and an ‘introductory price’ of $495 for Verifi.”

Insurance companies regularly review new technologies and treatments to make decisions about covering them. As the research file about the maternal blood tests grows, if the evidence of their accuracy is compelling, the tests eventually could be considered “standard.”

But that’s not their status today, and their worth must be determined on an individual case basis after frank and full discussion between the obstetrician and the parents.

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