Feb. 3--A year ago, a group of Abington fertility specialists became the first in the Philadelphia area to offer the ultimate in genetic selection.

In the three-stage process, embryos are created in a lab dish and tested for a particular genetic abnormality, and then only the normal ones are put in the woman's womb in the hope that one will take and she will become pregnant.

It is a costly, invasive, less-than-perfect way to stack the genetic deck. But for some couples at high risk of passing on terrible genetic diseases, it is a welcome option--far less traumatic than facing the choice between aborting a defective fetus and raising a sick child. "You're avoiding making horrible moral and ethical decisions [after fetal testing] at 14 weeks. You're preventing an abortion," said Stephen Somkuti, explaining why he and partners Jay S. Schinfeld and Larry I. Barmat wanted to offer the procedure, called preimplantation genetic diagnosis.

So far, after 25 cases, Abington Reproductive Medicine can claim two successes: a baby born without the gene for Huntington's disease, a deadly, degenerative brain ailment; and one born without the chromosomal abnormality for Klinefelter's syndrome, which causes infertility and learning disabilities in males.

But the doctors--along with their patients--acknowledge that rigging a baby's genetic inheritance could be a slippery ethical slope. Preimplantation genetic diagnosis was first accomplished 13 years ago, yet ethicists are still debating when its use is appropriate. Screening for a devastating disease is one thing, but what about for color blindness? Or gender? Or, someday, intelligence?

"A lot of this technology is being used by doctors and families who have a strong tradition of upholding the parents' choice," said Jeffrey Botkin, a pediatrician and ethicist at the University of Utah in Salt Lake City. "It really is opening the door so widely to fine-grain selection of children's traits."

In the United States--unlike Britain--fertility treatments are essentially unregulated, and patients willing to pay for a treatment can usually find it. The Abington group has decided it will not offer preimplantation embryo diagnosis for sex selection, except for a sex-linked genetic disease. But as more genes are discovered, the concept of designing babies with selected traits may not be far-fetched. "We here are pretty conservative, but the line in the sand is vague," Barmat said. "In the future, we may be doing [embryo screening] for many nonmedical reasons."

At this point, the issues are so emotional and controversial that only one local couple, Robert and Patricia Wunsche of Croydon, Bucks County, agreed to talk about using embryo diagnosis. Robert, 27, an accountant, inherited a rare skin disease, pachyonychia congenita, from his mother. It disfigures his fingernails and toenails (imagine nails with a fungal infection). Worse, it makes his skin so sensitive to pressure that after just a few hours of standing, painful calluses and blisters develop on his feet.

To avoid passing the disease on to a child, the Wunsches considered using donated sperm. Then they learned about the high-tech option at Abington Memorial Hospital. "There's a thin line between using science and playing God," said Patricia, 28, a medical billing specialist. "But it's not like we just want a better-looking child. Part of being a parent is wanting to do everything you can to keep your child from suffering."

Robert said: "There are cases where people just want to have [gender] balance and pick a boy over a girl. I don't agree with that. But if you're doing something to help a child be healthy, I don't see the problem."

Eight of the couple's nine embryos were found to have the pachyonychia gene defect, and the one healthy embryo died after being placed in Patricia's uterus. Now, the Wunsches are trying to save up the $15,000--including $4,000 for embryo diagnosis--that they need for another try. (Their health insurer, like most, won't cover it.)

Because of the ethical concerns, the technical challenges, and the costs, only about 100 centers around the world now offer preimplantation genetic diagnosis, and only about 1,000 babies have been born as a result. (Abington's closest counterparts are in northern New Jersey and Washington.) "Right now, this is still a research procedure," said Sandra Carson, a professor at Baylor College of Medicine in Houston and president of the American Society for Reproductive Medicine. "Its medical indications and ramifications are really not worked out yet."

The fact that it works at all reflects two amazing things: Each of the body's 100 trillion cells contains the complete human genetic code, and a microscopic three-day-old, eight-cell embryo can give up one or even two of its cells for genetic analysis and continue to develop normally.

The delicate process of removing an embryo cell--an embryo biopsy--leaves no room for error.

That's why the Abington doctors recruited embryologist Scott Smith from an Atlanta fertility clinic. Researchers do not yet know the long-term effects, if any, of embryo diagnosis, but "so far, the children born seem to be fine," Smith said.