Selecting Better Babies, and What Else?

Aug. 13 -- Diane Rinaldi was 36 years old when she and her husband decided to start a family. They tried for several years, struggling through four miscarriages.

"No one ever knew why I miscarried," Rinaldi told ABCNEWS correspondent John McKenzie. "They didn't have any true reason. They assumed it was genetic."

Then the Rinaldis learned of a new procedure called embryo screening that could dramatically improve their odds.

"It's probably the best and most important tool I have to help couples minimize the risk of miscarriage," said Dr. David Sable of St. Barnabas Medical Center in Livingston, N.J.

Before screening, couples first go through in vitro fertilization, mixing eggs and sperm in a lab, to create as many embryos as possible. Doctors then screen each embryo for defective chromosomes, so that only normal embryos are placed in the womb. The procedure provides three important benefits:

More Pregnancies: The process of eliminating embryos that cannot attach to the uterus results in a higher number of successful pregnancies.

Fewer Miscarriages: A lower number of babies are lost because they have been pre-screened for genetic defects associated with miscarriage.

Healthier Babies: By identifying chromosomes for Down Syndrome, Turner Syndrome and other disorders, the test can help ensure that the baby is healthier before it is implanted in the womb.

While embryo screening was introduced about a decade ago, it's only in the past few years that researchers have refined the technique so that now it detects about 70 percent of chromosome abnormalities. And typically only couples who are experiencing numerous miscarriages are having this screening done.

Ethical Concerns

However, as scientists continue to understand genetic coding, some question whether the ability to screen could lead to couples doing so for non-medical reasons.

"We can screen embryos to make sure they don't have chromosomal abnormalities that won't allow them to develop normally," said Jeffrey Kahn, director of the Center for Bioethics at the University of Minnesota. "But, I think it's very hard for us to draw the line about where the appropriate uses end and the unethical uses begin."