"The long-term consequences to the child are completely unknown," said Dr. William Hurlbut, consulting professor at the Neuroscience Institute at Stanford University Medical Center. "Something subtle but significant might be changed in the final physical frame or personality of the person born -- like tipping the rocket slightly on the launch pad, a tiny tilt might make some difference in the final destination.
"From a practical perspective I think this may cause some political stir, but I don't think it will be greeted as much of a solution."
Some researchers are looking at ways to create cloned embryos from adult cells and using the resulting embryos for research. To do this, they insert the genetic material of an adult cell into a human egg cell -- a similar technique used years ago to create Dolly, the cloned sheep.
The technique obviates the need for embryos, opting instead for human egg cells. And thanks to new research, scientists can now tap into the enormous pool of fertilized eggs created through IVF procedures, potentially using them to create clone embryos for stem cells.
"There are a half million fertilized eggs created every year in the U.S., and 3-10 percent of those will not develop," said Dr. Kevin Eggan of Harvard University's Stem Cell Institute, lead author of a recent study on the technique.
As with the other possibilities, the cells that are created cannot differentiate into the full range of tissues offered by embryonic stem cells. Researchers also worry that the political implications of these alternative developments could hinder the progress of the study of actual embryonic stem cells.
"It is important to note that the opponents of stem cell research will seize upon these studies as cause to stop funding human [embryonic stem] cell research...that these alternatives obviate the need to use embryos in research," Harvard's Daley said.