The Methods

The idea of pushing a blue or pink button and popping out a baby of choice is way off the mark. The biotechnology dictating how nature takes its course is much more complex, amazing, and flawed. Here's a look at what science has developed so far.

Preimplantation Genetic Diagnosis

WHAT IT IS: A technique that uses fluorescent color to identify the male and female chromosomes on embryonic cells.

HOW IT WORKS: Charles Strom, M.D., Ph.D., director of medical genetics at Illinois Masonic Medical Center, in Chicago, explains the procedure: "The woman takes a medication that causes her to make multiple eggs, which are then suctioned by needle from her ovaries. The eggs are placed on tissue culture plates, where they are fertilized with sperm  -- usually the husband's  -- a routine procedure for in vitro fertilization. Then the embryos are grown in a test tube until they have multiplied to five to ten cells, which takes about two days. A single cell from each embryo is analyzed, using a technique that attaches fluorescent probes to specific DNA sequences. If it's a male, you have one green strand and one red strand of DNA; if it's a female, both strands are green." Once the sex has been determined, the doctor implants two or three embryos of the chosen gender into the woman's uterus.

SUCCESS RATE: Determining the sex through this procedure is close to 100 percent reliable. There is no guarantee, however, that implantation will work.

WHO IS ELIGIBLE: This method is only available to couples who have a hereditary disease in the family.

COST: $10,000 for in vitro fertilization plus $2,500 for preimplantation diagnosis per menstrual cycle (it can take at least two or three menstrual cycles for a woman to conceive).

RESOURCES: There are approximately 30 centers in the world  -- about a fifth of which are in the United States. Go to www.genetests.org.

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