A university researcher in Washington has, as an experiment, cloned human embryos, splitting single embryos into identical twins or triplets. This appears to be the first report of such a feat.
The scientist, Dr. Jerry L. Hall of George Washington University Medical Center, reported his work at a recent meeting of the American Fertility Society.
The experiment was not a technical breakthrough, since he used methods that are commonly used to clone animal embryos, but it opens a range of practical and ethical questions.
For example, since human embryos can be frozen and used at a later date, it could be possible for parents to have a child and then, years later, use a cloned, frozen embryo to give birth to an identical twin.
Dr. Hall is in the in vitro fertilization program at George Washington University, in which doctors help women have babies by mixing sperm and eggs in a laboratory and then implanting the embryos in the women.
He was trying to devise a method to create more embryos to implant when couples do not produce a sufficient number for fertilization. The embryos used in the experiment were at the stage of just a few cells. They were not usable for technical reasons and were discarded, not implanted in a woman's womb.
Dr. Hall and Dr. Robert Stillman, the director of the in vitro fertilization program, declined to be interviewed. But in a summary of a scientific paper Dr. Hall presented on Oct. 13 at a meeting in Montreal of the American Fertility Society, he wrote that by splitting the embryos into twins or triplets or quadruplets, doctors could try to implant more embryos, making it more probable that the woman would become pregnant with at least one of them.
The process would increase the chances of multiple births, as does any in vitro fertilization.
Dr. Hall reported his findings at an open meeting, but his results were not publicized. A description of them is to appear next week in a news article in Science magazine.
Cloning, the creation of organisms with an identical set of genes, occurs naturally in humans in the case of identical twins.
A technique has been developed for making identical twins in animals like cattle by dividing the embryo one or more times and letting the new clusters of cells develop into genetically identical organisms.
Scientists who routinely clone animal embryos said that cloning human embryos should be just as easy.
"I see no reason on earth why it could not be done," said Dr. Robert McKinnell, a professor of genetics and cell biology at the University of Minnesota.
Dr. McKinnell explained that it is much harder to take a cell from an adult and use it to make embryos or even clones, since the cells of adult organisms are committed to specific functions and have switched off their capacity for full development.
Biologists do not yet understand how to reverse these switches. the laboratory, plants can be cloned from a single cell of an adult plant, but no way of doing this with mammals has been discovered.
"If you live to be 100, a liver is a liver and it doesn't turn into brain and it doesn't turn into muscle," Dr. McKinnell said.
Ease is troublesome
Ethicists said that the very fact that cloning embryos is easy makes the question so intriguing.
"It's not scientifically rich, but that's what makes it morally and legally of concern," said Dr. Arthur Caplan, director of the Center for Bioethics at the University of Minnesota. "It doesn't take a Nobel Prize team with a million-dollar lab."
Despite the scruples of most scientists, he said, there is no way to control or contain the technology.
The ethical implications are perplexing, experts said.
One "Brave New World" scenario made possible by embryo cloning is that parents might be able to save identical copies of embryos so that, if their child ever needed an organ transplant, the mother could give birth to the child's identical twin, a perfect match for organ donation.
Or parents could keep a frozen embryo as a backup in case their child died.
Several infertility experts, who run in vitro fertilization programs, said they have no intention of cloning human embryos.
In fact, said Dr. David Meldrum, the director of the Center for Advanced Reproduction in Redondo Beach, Calif., it would have been better if Dr. Hall's experiment had never been discussed.
"It is not a good thing to talk about cloning human embryos," he said."The public, I think, feels uncomfortable with meddling with the life-producing process. They will see this as one more step along a slippery slope toward more and more meddling."
Yet now that the cloning of human embryos is clearly a possibility, some are asking why it has started with a whisper and not a shout.
The answer seems to be that the cloning of humans is part of the nether world of in vitro fertilization, a research area that the government has decided to forsake.
With no federal money to pay for the research, studies of in vitro fertilization have been carried out by scientist-entrepreneurs, many of whom left government laboratories to work on their own, the only way they could study human embryos.
Although they have made spectacular advances in the 15 years since the first child was born from in vitro fertilization, no national board has debated or even discussed the ethical issues.