Peering into the genetic code of an eight-cell creature scarcely stirs excitement anymore in labs across America. But when the eight-cell creature is a human embryo -- an egg and sperm united in a petri dish just 72 hours before -- the sight of chromosomes lighted up in neat, color-coded pairs stirs excitement, and something deeper as well.
It stirs hope.
This is preimplantation genetic diagnosis, fertility's new frontier, where advanced genetics meets the thriving science and booming business of in vitro fertilization.
Twenty-five years after the birth of the first child conceived by human egg and sperm in a laboratory, preimplantation genetic diagnosis -- or PGD -- is touted as the next big thing: a technology that could eliminate inherited diseases, boost birth rates among infertile couples for whom nothing else has worked and reduce the incidence of potentially risky multiple births.
"I see this as a trend for the future, and I do see that in the future, every embryo [produced in the course of IVF cycles] will be tested," says Dr. Harvey Stern, head of the Genetics and IVF Institute's PGD program in Fairfax, Va.
To the dismay of ethicists, however, PGD may open the door to a "new eugenics," as parents seize an emerging opportunity to customize their babies for anything from tissue type to eye color, broad shoulders to extreme intelligence.
A process of detecting genetic abnormalities in embryos while they are still in a lab's incubator, PGD allows a couple to choose embryos free of evident flaws for transfer into a woman's uterus. For many who suffer from or carry the gene for an inherited disease, PGD offers the promise of a baby free of a known stalker. For many among the infertile, it offers a better prospect that an embryo will take hold, result in pregnancy and produce a healthy baby. For some opposed to abortion, it allows "choice" to occur before a pregnancy begins.
For the nation's roughly 400 fertility doctors, PGD -- and a related technique called aneuploidy screening -- brings in a new and fertile class of patient (genetic disease carriers) and offers a new service to infertility patients who have failed with lesser therapies.
BEYOND that, the procedure, which costs about $3,500 to $4,000, offers fertility clinics a lure that in this swift-moving and highly competitive field they cannot refuse: better pregnancy rates. While PGD's early successes in delivering on that promise have been modest, its champions see improvements on the horizon that will make it more effective and more widespread in the next few years.
Around the world, about 1,000 babies have been born following PGD, making it a procedure still in its infancy next to IVF, with roughly a million births worldwide. But PGD already is being used to help would-be parents choose the gender of a child and to weed out embryos that would carry any one of nearly 60 inheritable diseases, from early-onset Alzheimer's to Huntington's disease.
The ability to screen for a wider range of things is certain to follow, as scientists identify with ever-greater precision the role of genes in transmitting across generations everything from mental illness and physical afflictions to temperament and physical traits.
But as that becomes possible, some question how far the process should go. In early July, an Australian fertility clinic announced that it had used PGD to screen out embryos carrying a gene that would predispose its carriers to deafness. The newest application for PGD prompted an outcry from disabilities activists, who noted that deafness is neither life-threatening nor a certainty for those who carry the gene. They argued that if PGD were to come into wide use for such purposes, it could drive down the deaf population and isolate a thriving culture.
Ethicists, meanwhile, fear that this latest use of PGD could make the trivial use of such powerful technologies easier to contemplate.
"If you give people the idea that it's perfectly OK -- and doable -- to pick out this, that and the other trait" in an embryo, "then you're opening the door to shopping for babies as accessories to your life," says Marcy Darnovsky, an analyst with the Center for Genetics and Society in Oakland. "You're on the way to designer babies right there."
Already, concerns about the implication of the technology has prompted several countries -- Austria, Germany, Ireland and Switzerland -- to outlaw the PGD procedure. France, Belgium, the Netherlands and Italy all have adopted regulations limiting its use. The United Kingdom, after an extraordinary national debate in 2001, has placed a range of restrictions on PGD providers, including a ban on the procedure's use for gender selection.