Checkups For Embryos

For three years the empty nursery has been filled only with hopes and dreams for Tanja and Kurt Weber.

They always wanted a big family, but as CBS News Correspondent Elizabeth Kaledin reports, fate had something else in store

"Its really hard when you try for so long to get pregnant," says Tanja Weber.

Tanja carries a rare genetic defect in which some chromosomes line up in the wrong place. The result has been miscarriages, the likelihood of severe birth defects and endless heartbreak.

"I wouldn't wish this on my worst enemy," says Tanja Weber.

But because doctors know what this defect looks like in a developing embryo, the Webers decided to rely on genetic testing to do something Mother Nature couldn't.

It's called pre-implantation genetic diagnosis, or PGD, in which embryos developed in fertility clinics are screened for genetic problems before being implanted in the mother.

Experts like Richard Scott say the science has evolved from brave new world to standard practice.

"In 1995 there were probably a few dozen cases done in the U.S.," says Scott. "In 2003 there were thousands of cases."

Using a color-coded computer system, technicians can look deep inside developing embryos to see if all chromosomes are in place for a healthy baby.

In the Weber's case, doctors looked for the specific genetic defect and found it. They implanted only healthy embryos in Tanja. Now, a baby boy is expected in February.

"It eliminates, or very nearly eliminates, the risk of having an abnormal child," says Scott. "Which one of us would not choose to have a normal child if given the choice."

But critics liken PGD to playing God - picking which embryos will live and which will die.

It is a largely unregulated field with the potential to be misused for non-medical reasons.

"It's perfectly legal for a patient to go to a fertility clinic and say, 'I'm perfectly fertile, I just want to make sure my next child is a girl,'" says Lee Silver, a professor of genetics at Princeton University.

What's next? Many wonder it could be selecting embryos for intelligence or beauty. Leaders in the field say it's still science fiction.

"We still don't know what complex of gene codes for intelligence, code for great beauty, so we wouldn't even know which genes to try and control in that process," says Scott.

"This technology is going to progress very, very slowly," says Silver. "Society is going to decide where to draw the line."

For the Webers, the technology has been nothing more than a gift - preventing more anguish. While helping them realize one of life's simplest dreams.

"It's not like we're doing it for a frivolous reason," says Kurt Weber. "We're doing it to have a healthy child that could grow up in a loving home with a loving family."