Research on mice suggests new fertility treatments

The technique also raises a host of medical and ethical concerns.

"I would be worried about the safety of trying to make kids this way," said Lawrence Goldstein, director of the stem cell program at the University of California, San Diego. "It seems like an experiment on those kids."

It would also be complicated and expensive, adding to the question of whether it would really be a good way to treat infertility, he said.

He and others also said society will have to decide how much government regulation would be needed, both for the initial research in humans and its routine use by doctors.

For example, the new work moves scientists closer to the possibility of tinkering with genes that would affect not only one person but also be inherited by future generations, which has long been controversial, said Dr. George Daley of the Harvard Stem Cell Institute. And basic research with such eggs could mean making and destroying human embryos in the lab, which many people oppose.

More controversy could arise over using the method for women who are infertile simply because of their age.

"Society is not clear about how it feels about older women having children," said Josephine Johnston of the Hastings Center, a bioethics research institute in Garrison, N.Y. She said there has been no sustained public discussion of "how old is too old, and what does that even mean."

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Journal Science: http://www.sciencemag.org

Malcolm Ritter can be followed at http://www.twitter.com/malcolmritter