Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, July 31, 1990 TAG: 9007310130
SECTION: NATIONAL/INTERNATIONAL PAGE: A-1 EDITION: METRO
SOURCE: Los Angeles Times
DATELINE: LENGTH: Medium
The new technique, the doctors say, eventually could make it possible to eliminate genetic defects in treated families, and in many cases also avoid the need for women to undergo a therapeutic abortion after the fetus is found to have a serious defect.
The twin girls were born nearly two weeks ago at Hammersmith Hospital in London to a mother who was the carrier of a gene for a fatal genetic defect that strikes only boys, Dr. Alan Handyside of the Royal Postgraduate Medical School at Hammersmith said Monday in a telephone interview.
Handyside and Dr. Norman Winston artificially fertilized eggs collected from the mother, Debbie Edwards, 29, and grew them in the laboratory until each egg had divided into eight cells, which is the smallest size from which a single cell can be removed without risk to the embryo. Using a newly developed procedure, they then removed one cell from the fetus and used it to determine the embryo's sex.
Male embryos were discarded and female embryos were implanted in the mother's womb. The newborn girls are apparently completely healthy. Three similar births are expected over the next six weeks. The Hammersmith group plans to extend the work to 50 more couples over the next few months.
"It's a very exciting first step" in developing new ways to detect birth defects, said geneticist Yuri Verlinski of the Illinois Masonic Medical Center in Chicago.
"This . . . should have a huge social impact over the next two decades," Winston said.
Conventional prenatal analysis is now carried out in the 10th to the 16th week of pregnancy by collecting fetal cells from either the amniotic fluid that surrounds and cushions the fetus in the womb or from the chorionic villi, hairlike protrusions on the surface of the placenta.
When those tests show a serious genetic defect, many parents choose an abortion. But those abortions can be quite traumatic because the mother has already invested great energy in carrying the fetus and has often been able to feel it moving in the womb.
The technique, "offers couples at risk an alternative that avoids some of the emotional distress caused by prenatal diagnosis later in pregnancy," said ethicist Kathleen Nolan of the Hastings Center in Briarcliff Manor, N.Y.
The researchers also are extending the technique so that it can be used to screen in the test tube for any genetic defect - not just those that affect only one sex.
Handyside noted that within 12 months, they will be able to screen embryos for specific genetic defects. That will require refining chemical techniques for multiplying the DNA, which is deoxyribonucleic acid, the blueprint of life, to large enough quantities for conventional screening.
Using those techniques, they would then be able to screen for any particular type of genetic defect and implant only the healthy embryos in the mother's womb.
by CNB