WASHINGTON -- In politics, it always helps to put a face on a cause.
For supporters of embryonic stem cell research, nobody played that role quite like Christopher Reeve, the paralyzed actor who touted the promise of such research before his death in October.
Opponents of embryonic stem cell research also have found their face, 21 of them. They are the children who helped President Bush show what a frozen embryo has the potential to become.
''The children here today remind us that there is no such thing as a spare embryo," Bush said last month at the White House.
The embryos that would become these children were created through in vitro fertilization and placed in frozen storage. They were donated by couples who no longer needed them to add to their families, were shipped overnight, and eventually implanted in a woman who some nine months later became their birth mother.
So far, 81 ''snowflake" babies have been born through embryo adoption, the president noted.
''We hear a lot of rhetoric that these are just clumps of cells," said Dr. David Prentice, a senior fellow at the conservative Family Research Council. ''The snowflake kids are very effective in showing that they are very young humans that need to be given their chance for development."
Over the past two decades, since the first ''test-tube baby" was born, an estimated 400,000 frozen embryos have accumulated in more than 400 fertility clinics around the country. What to do with those frozen embryos has become a matter of intense debate.
Some advocate donating excess embryos for stem cell research.
Embryonic stem cells are master cells that form during the early days after conception and can turn into any tissue in the body. Scientists hope one day to harness them to grow replacement tissue to treat diabetes, Parkinson's disease, spinal cord injuries, and other diseases.
However, obtaining those stem cells kills the embryo. Thus some religious groups and conservatives oppose creating embryonic stem cells for research. Bush has banned the use of federal funds for research on stem cell lines created after Aug. 9, 2001.
Some stem cell research opponents say excess embryos could be donated to some of the 6 million to 7 million infertile couples in the United States.
''There is an opportunity to give every one of these embryos an adoptive set of parents," Prentice said.
The government does not track the number of embryos donated to other couples and brought into the world as babies. However, it is undoubtedly a tiny fraction of the embryos that have been frozen.
A Rand Institute survey conducted two years ago said 88 percent of embryos have been designated by couples for family building. The leaves 12 percent for an array of other uses including research, donation, or discarding.
Bob and Angie Deacon of Virginia Beach, Va., believe they had only one option for the 13 embryos they created more than six years ago -- giving them to another couple. The Deacons had twins after in vitro fertilization, and a doctor recommended they have no more children.
For years, they wondered how to deal with the leftover embryos, but then they heard about Nightlight Christian Adoptions, which coined the term snowflakes for children born through embryo donation.
''The story for me was just very touching. I just knew that was something I needed to do," Angie said. ''I didn't want them used for research, I didn't want to thaw them out, just destroy them. I believe life begins at conception."
The Deacons have yet to be matched up with another couple. When they are, the couples will exchange pictures, a family history, and essays. They can choose to have as much or as little contact as they want.
Pamela Madsen and her husband, Kai, who have two children, have chosen another route for their frozen embryos.
''Giving them to stem cell research may not help a child be born, but it may help a child lead a better life," said Madsen, executive director of the American Fertility Association in New York, an advocacy group for families struggling with infertility.
Madsen said she was uncomfortable with the idea of donating the embryos to another couple.
''It would be a full sibling," she said. ''That raises very complicated questions for our children and for that child."
Dr. Brad Van Voorhis, director of reproductive endocrinology and infertility at the University of Iowa, said Madsen's view is not uncommon.
When the university in the late 1990s surveyed 365 couples about what they wanted to do with embryos that had been frozen for more than two years, about 44 percent wanted to continue storage.
Among the remaining couples, 34 percent wanted to discard the embryos, 10 percent wanted to donate them for research, and 12 percent wanted to donate them to other couples.
Van Voorhis said he supports embryo donation but that it is not the only option.
''Donation for research is a very worthwhile and viable option for the embryo as well," he said.
He said he uses the term embryo donation rather than adoption, because adoption means home studies, physical screenings, and counseling. Instead, the embryos are allocated on a first-come, first-serve basis, with childless couples getting additional preference. The word adoption also gives the impression that an embryo is a human being.
''An embryo deserves great respect, but not the respect accorded actual persons," Van Voorhis said.
Nightlight Christian Adoptions said it has not sought to align itself in the fight against embryonic stem cell research, but it does not mind the attention if that is what it takes to advertise their program to the public.
''We're not seeking the political limelight, but if these 81 children, with 17 more on the way, get the message out . . . then I'm very happy about that," said Lori Maze, director of the snowflakes program.