Genetic test on embryos stirs debate

As Chad Kingsbury watches his daughter playing at their suburban Chicago home, the thought that has flashed through his mind a million times in her two years of life recurs: Chloe will never be sick.

Not, at least, with the inherited form of colon cancer that has devastated his family, killing his mother, her father and her two brothers, and that he too may face because of a genetic mutation that makes him susceptible.

By subjecting Chloe to a genetic test when she was an eight-cell embryo in a petri dish, Kingsbury and his wife, Colby, were able to determine she did not harbor the defective gene. That was the reason they selected her, from among the other embryos they had conceived through elective in-vitro fertilization, to implant in her mother's uterus.

Prospective parents have been using the procedure, preimplantation genetic diagnosis, for more than a decade to screen for genes certain to cause childhood diseases that are severe and untreatable.

Now more couples are using preimplantation genetic diagnosis to detect a predisposition to cancers that may or may not develop later in life.

For most parents who have used preimplantation diagnosis, the burden of playing God has been trumped by the near certainty that diseases such as cystic fibrosis and sickle-cell anemia will afflict the children who carry the genetic mutation that causes them.

Couples like the Kingsburys face a more complex calibration. They must weigh whether their desire to prevent suffering from a cancer that is not certain to occur justifies the conscious selection of an embryo and the implicit rejection of those that carry the defective gene.

Failure to detect

In addition, the test is not completely effective: There is up to a 3 percent chance preimplantation genetic diagnosis will fail to detect an unwanted mutation.

If the growing interest in screening for cancer risk signals an expanded tolerance for genetic selection, geneticists and fertility experts say it may be accompanied by the greater use of preimplantation diagnosis to select for characteristics that range from less serious diseases to purely matters of preference.

The process is difficult and expensive. Preimplantation genetic diagnosis, which requires in-vitro fertilization, can cost tens of thousands of dollars.

While insurance companies often pay for the more traditional uses of the procedure, they have not done so for cancer-risk genes, fertility experts say.

The barrier to affordability, some critics fear, could make preimplantation diagnosis for cancer risk the first significant step toward a genetic class divide in which the wealthy will become more genetically pure than the poor.

Prospective parents who want to avail themselves of preimplantation genetic diagnosis must first undergo the same in-vitro fertilization process often used to assist infertile couples, in which eggs are extracted from the mother and fertilized with the father's sperm in a petri dish.

High cost, concerns

When the resulting embryos are three days old, doctors remove a single cell from each and analyze its DNA. Only embryos without the defective gene are then considered candidates to implant in the mother's uterus.

The out-of-pocket costs often exceed $25,000. Despite the birth of thousands of apparently healthy babies after preimplantation genetic diagnosis, there is still concern the long-term effects of removing a cell from an eight-cell embryo have not been studied enough.

Familiarity with their own genetic profile makes some more comfortable with the testing. For them, genetic traits can seem less like destiny and more like any other part of their lives that can be improved by technology.

But the same knowledge makes others who carry the mutations take particular offense at the selection procedure, which they say implies they themselves, and many members of their family, should never have existed. It raises the specter of eugenics, they say.

Other critics oppose preimplantation diagnosis on the grounds it could be used to select against homosexuals, women or people with disabilities.

Proponents of the technology say confusing the concept of "designer babies" with people trying to avoid deadly illnesses is hurtful and misleading.

As it becomes easier to identify the possible consequences of more kinds of genes, the decisions for parents may become harder. Having passed over four embryos with the defective gene and identified 10 healthy ones, the Kingsburys were asked if they wanted to pay $2,000 extra to test them for Down syndrome. That test eliminated two more.

"You kind of feel like you shouldn't be doing it," Colby Kingsbury said. "But then why would we go through all of this and not take those extra precautions?"