Babies by design
Will mastering genetic disorders lead to 'master race'?
January 4, 2000
From Medical Correspondent Rhonda Rowland
(CNN) -- In the future, when couples decide to have babies, they may start with science instead of sex.
By the year 2003, scientists expect to finish mapping the human genome. That should give researchers unprecedented information about thousands of inherited disorders and increase the ability of doctors to screen for disease -- even before conception.
This same genetic information might be used by prospective parents to find out a range of traits an embryo has, such as eye and hair color, height, intelligence and life expectancy. And that means making complex choices about which embryos to implant in the mother's womb.
"We will, I'm sure, have the ability to increase the number of male babies being born or female babies being born, or blond babies," said Dr. Nathan Slotnick, a geneticist at Eastern Virginia Medical School.
Slotnick said that as the ability to predict traits expands, it will change the very nature of reproduction.
Sam Strickland and Mandy Lemke's son was born with a chromosomal disorder known as trisome 18. Instead of the usual two chromosome 18s, he had three.
"Over half the children (with the disorder) have very severe heart disease, said Dr. Paul Fernhoff, an Emory University genetics specialist. "Many others have kidney problems and others (have defects) in the way their fingers and toes are shaped."
A routine blood screening test given early in Lemke's pregnancy failed to pick up the problem. The defect proved fatal for her son.
Strickland and Lemke now say they won't leave their next pregnancy to chance. And they won't have to.
A new technology introduced in the mid-1990s allows doctors to do limited analysis of an embryo's genes in a laboratory, screening out those that may have defects. The procedure is called pre-implantation genetic diagnosis, or PGD.
After she had several miscarriages, Barb Rueth and her husband, Rich, turned to Reproductive Biology Associates of Atlanta. Doctors there suspected chromosomal defects and suggested that the couple consider PGD.
"They explained it as a way to look at each of the embryos to find out maybe some of the reasons why we'd had miscarriages," Barb Rueth said.
Couples electing PGD must use in vitro fertilization. In this process, the sperm and eggs are matched and incubated in a laboratory. When the embryos are three days old, and consist of just eight cells, one of those cells is removed and analyzed for abnormalities. Those embryos that appear healthy and free of genetic defects are implanted in the woman's uterus.
"Right now the technology is somewhat limited," said Dr. Hilton Kort of Reproductive Biology Associates. "We're able to look for trisome abnormalities, which are the commonest abnormalities -- Down's syndrome being one of those -- and other chromosomal abnormalities."
The first time the Rueths underwent the PGD procedure it resulted in eight embryos. Only one was found to be free of chromosomal defects and it did not result in a pregnancy. Still, the couple has no regrets.
"If you can decrease your odds of discontinuing the heartache and disappointments ... I think there's not a couple that wouldn't go that route," said Rich Rueth.
The Rueths tried PGD again and got three embryos -- too few to risk genetic testing. They decided to go ahead with implantation anyway. Their baby is due in January.
"This was our special baby, our miracle baby, if it has special needs, that was the way it was going to be," said Barb Rueth.
Only about 300 babies have been born worldwide with the help of PGD. The oldest children are 3 to 4 years old and all appear healthy.
Other research could improve genetic screening techniques like PGD so that couples could learn about potential genetic problems even earlier. For example, scientists at the University of Massachusetts are testing sperm and examining its genetic makeup before it's mixed with eggs.
"I think that looking years into the future we might very well treat all human genetic disease in the fetus," said Dr. Alan Flake with Children's Hospital of Philadelphia.
Procedures like PGD also can tell parents which embryos will produce boys and which will grow into girls. The cost of the tests -- some as much as $10,000 a try -- likely will keep them from becoming a routine way for selecting the gender of babies.
But some scientists worry that the procedures will one day become commonplace. They also worry that screening out disease like breast cancer may screen out embryos that might have grown into highly productive people.
"This particular embryo, which is at risk for breast cancer, that woman may go on to be a fantastic artist, pianist, scientist, may discover the cure for cancer," said Kort.
Dr. French Anderson of the University of Southern California, who some consider the father of gene therapy, wants fetal gene therapy only to be used to cure disease.
"The only protection society has from a slippery slope that basically leads to a Gattaca type environment -- designer babies, a master race -- is public scrutiny," Anderson said, referring to the 1997 film where babies are genetically engineered.
Scientists also worry about the impact of manipulating genes on the gene pool. Anytime a new gene is used to alter an embryo, it has the potential to change the genetics of generations to come.
"It is a short step to go from selecting virtual children, selecting each embryo which is implanted, to thinking, well, why not go in and do an extra step and so some sort of genetic enhancement," said Dr. Gregory Stock with the Program on Medicine, Technology and Society at UCLA.
Human Genome Project - Mapping ourselves
University of Massachusetts Medical School
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