DOCTORS AT THE ILLINOIS Masonic Medical Center in Chicago have pioneered a test to help women undergoing in vitro fertilization avoid carrying a child with Down's syndrome. If one of their eggs appears to carry the extra chromosome associated with Down's, it's simply not transferred to the womb.

According to a team led by Dr. Yury Verlinsky, director of the center's Reproductive Genetics Institute, the extra chromosome can be detected by examining the "polar body," a sac that is cast off by the egg and carries a mirror image of its chromosomes. Of the 6 babies and more than 20 ongoing pregnancies since the trial began, none has Down's. Now, Illinois Masonic is recruiting other hospitals to help establish statistically that the test works.

Illinois Masonic plans to charge $2,000 to $3,000 for the test, on top of the $7,000 or more for ordinary in vitro fertilization. The test won't rule out Down's syndrome entirely, since in about 5% of cases the extra chromosome originates with the sperm, not the egg.

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