Should Age Determine Prenatal Testing?
Study Challenges Long-Held Practice of Reserving Tests Mostly for Women 35 and Older
But either test -- typically costing about $1,000 -- can also slightly boost miscarriage risk, which is why they're usually not recommended for younger women unless they are deemed higher risk of birthing a baby with Down syndrome. In amniocentesis, done between 14 and 18 weeks of pregnancy, a needle is inserted into the womb and a small amount of fluid that surrounds the fetus is withdrawn for chromosomal testing. With chorionic villus sampling (CVS), which can be done several weeks earlier, a needle is passed into the womb to remove and examine a small amount of tissue in the placenta.
In this study, Kuppermann and her colleagues at the University of California, San Francisco, did a cost-utility analysis of either getting or not getting the two prenatal tests in 534 pregnant women between ages 16 and 47. This analysis measured several factors -- the cost and effectiveness of the tests against the risk of miscarriage and benefits of detecting a fetal chromosomal abnormality. The women studied preferred procedure-related miscarriage risks to having a baby with Down syndrome.
All age groups had a similar cost-effectiveness based on quality-of-life years gained from information from the test - that is, knowing before birth whether the baby had Down syndrome or another condition.
"Some interventions are life-saving and have no impact on the quality of life," Kuppermann tells WebMD. "Some might be life-saving and also impact quality of life. Some have no effect on life expectancy, but have a huge affect on the quality of life. These prenatal tests are in the latter category."
But at least one expert, who wrote an accompanying editorial to Kuppermann's study, tells WebMD that these calculations were made without making some important considerations.
"I have concerns about the failure to recognize that the unborn child diagnosed with a chromosomal abnormality has the potential to produce future benefits, while only recognizing it has the potential to incur future costs," says Stavros Petrou, PhD, health economist at the University of Oxford.
"I am also concerned about the failure to compare the cost-effectiveness of universal prenatal diagnostic testing against some of the screening programs currently available in most industrialized nations," he tells WebMD.
One alternative being investigated combines tests for certain biological markers in the blood and ultrasound measurement of what's known as nuchal translucency -- thickness of skin behind the fetus' neck. In one study presented two years ago before the Society for Maternal-Fetal Medicine, researchers reported that these measures detected with 85% accuracy whether a fetus had the chromosomal abnormality that causes Down syndrome. By comparison, certain tests, such as one that screens for high amounts of alfa fetal protein (a red flag for fetal abnormality), identify only 65% of cases and falsely ID about 5% of women, they said.