"Several features on
ultrasound scans that doctors thought were warning signs of
Down syndrome are almost always harmless, leading many women with normal fetuses to undergo unnecessary
amniocentesis, researchers say....
Researchers looked at seven markers sometimes spotted on ultrasound scans that are thought to increase the risk of Down. Only one of those markers--a shaded area suggesting a thickening at the back of the neck--was found to be a reliable indicator. The six other markers were certain brain cysts, shortened thigh and upper-arm bones, bright spots on the bowel or heart, and high fluid levels in the kidneys. About 10 percent to 14 percent of pregnant women have one of these markers, but fewer than 1 percent have Down babies. Ultrasounds that show an obvious structural abnormality, such as heart defects that are common in Down syndrome, should not be discounted.
In 1998, the latest year for which figures are available, 112,778 amniocenteses and 2.5 million
ultrasounds were performed in the United States.
The risks of miscarriage from amniocentesis are greater than the risks that a woman with normal blood tests but one of the ultrasound markers will have a Down syndrome baby, according to the analysis." emphasis mine
Reference:
- AP wire service report, Nov. 23, 2000