New genetic test for selecting healthy embryos
Last Updated: Monday, June 19, 2006 | 3:15 PM ET
CBC News
British scientists have come up with a much broader way to allow couples to screen test-tube embryos for a wide range of genetic disease. But ethicists have raised the concern that this new technique could someday allow parents to pick and choose their offspring, and to reject certain embryos for potential ailments that may never materialize.
Current screening tests for pre-implantation embryos allow scientists to look for a particular mutation, such as the gene for cystic fibrosis or Tay Sachs, before an embryo is implanted using in vitro fertilization. The new technology, called pre-implantation genetic haplotyping or PGH, allows doctors to check for many more potential illnesses in an embryo, said Alison Lashwood of Guy's and St Thomas' NHS Foundation Trust in London, where the test was developed.
It could give parents more information about what embryo to use, said the researchers, who presented their findings on Monday at a European fertility conference.
While previous tests looked for a specific mutation in one gene linked to an inherited disease, the new test is broader, looking at all the DNA fingerprints or markers near the gene. Both types of tests screen embryos before they are implanted in a womb and can be seen as different from prenatal testing, which tests a fetus that may be aborted.
So far, researchers have tried the test on seven women, five of whom are now pregnant. They were testing for cystic fibrosis, an inherited disease that affects the lungs and digestive system, and Duchenne muscular dystrophy, a degenerative muscle disorder in males.
Embryonic testing raises ethical concerns for people holding strong views about the status of embryos, since leftover embryos are usually destroyed.
Where to draw the line?
Some people may feel comfortable with the idea of avoiding a serious disease that occurs early in life, but where should society draw the line along the ethical continuum, asks Tim Caulfield, a medical ethicist at the University of Alberta.
"What about selecting embryos that have just a predisposition for disease, say late-onset cancer or breast cancer or Huntington's disease, or perhaps using this technology to select things like eye and hair colour?" Caulfield said on CBC Newsworld.
Canada lacks formal rules on what kind of pre-implantation testing is allowed; internationally, most professional guidelines limit its use to screening for serious disease. No respectable lab in Canada would allow it to be used for cosmetic traits, said Dr. Edmond Lemire, a medical geneticist at the University of Saskatchewan. The issue is relevant to Canadians, given that Health Canada now licenses clinics, Caulfield said. The department released a consultation paper on pre-implantation screening last fall, which also raises the issue of the state's involvement in reproductive decisions, he added.