SCIENCE / MEDICINE : Prenatal Test for Birth Defects Found Safe

A prenatal test that can identify Down’s syndrome and other birth defects as early as the eighth week of pregnancy is safe and accurate, according to a nationwide, government-sponsored study.

The new technique is called chorionic villus sampling or CVS. It has been done on a limited basis in the United States since 1983, but this is the first study to carefully assess its safety and accuracy, said Dr. George Rhoads of the National Institute of Child Health and Human Development, which coordinated the study.

Dr. Laird Jackson of Thomas Jefferson University in Philadelphia presented the study’s findings in Boston at the annual meeting of the American College of Obstetricians and Gynecologists.

He predicted that CVS might one day largely replace amniocentesis, the current method of obtaining genetic information on a developing fetus. Amniocentesis, in which amniotic fluid surrounding the fetus is analyzed for chromosome abnormalities, cannot be done until the 16th week of pregnancy.

In chorionic villus sampling, doctors snip off a tiny piece of chorionic villus tissue, which grows from an enveloping membrane that eventually gives rise to the placenta. This can be done at seven to nine weeks.