A Utah doctor has pioneered a technique for safely determining whether an unborn child carries the genetic burden of Down syndrome.

Down syndrome is a frequently severe form of mental retardation. Often accompanied by physical debilities, it is often linked to the age of the mother. The older the woman, the more likely she is to have a Down syndrome child.Because Down syndrome is one of the great tragedies that can strike a family, many pregnant women want to know whether their unborn children have the disorder. But until now some - even high-risk women in their 40s - were reluctant to use the only technique that could give them answers.

That technique was amniocentesis, in which a hollow needle is used to draw out amniotic fluid for analysis. However, amniocentesis can cause miscarriages.

But now Dr. Greggory R. DeVore and an associate, Dr. Omar Alfi, have developed an ultrasound technique that allows doctors to determine whether a fetus has Down syndrome. Ultrasound is a noninvasive technique that uses sound waves to produce a picture of a fetus.

An article published Wednesday in the medical journal Obstetrics & Gynecology, written by DeVore and Alfi, describes the new color Doppler ultrasound.

"In the United States, between 30 and 40 percent of patients who are at risk are fearful of amniocentesis," said DeVore, who has a medical practice in Salt Lake City as well as in Pasadena and Tarzana, Calif.

"They don't have it done . . . They are very anxious and very concerned."

In their study, DeVore and Alfi discovered that they could detect 87 percent of Down syndrome among fetuses examined. The study was carried out in 1991, and the results are almost as good as those for amniocentesis, which detects virtually all Down abnormalities.

"The good news is . . . in our most recent data, our identification rate for Down syndrome is 96 percent," DeVore told the Deseret News in a telephone interview. The reason for the change is that the researchers have been able to increase the sensitivity of their instruments.

What is it about the Down's fetus that can show up on an ultrasound view as different from a normal fetus? "The heart is the key thing," he said. About 60 percent of Down syndrome children have heart defects. The color Doppler ultrasound shows the heart in great detail.

"It shows us the blood flowing through the heart chambers, in color," he said.

When this abnormality is combined with other physical differences caused by Down syndrome, the detection rate is exceptionably high.