JANICE PEARSE, a nurse in Baltimore, Md., recalls her long quest to become pregnant using in vitro fertilization.e
The first time her eggs were mixed with her husband's sperm in a petri dish, and the doctor told her that embryos had been formed, was an exhilarating moment, because "it's the closest to having a baby you've ever been," she said.
But for every experimentally created embryo that is successfully implanted - and Pearse was one of the lucky ones who eventually became pregnant - thousands of unneeded embryos are frozen in storage or discarded.
If it is acceptable to create an embryo for transfer into a woman's uterus - as is now done in fertility clinics - is it ethical to experiment on an embryo in the lab? Or just throw it away?
These are among the troubling aspects of the new frontier of medical science known as human embryo research.
Many scientists believe that studying the human embryo - at one week a cluster of cells no bigger than the period at the end of this sentence - could yield infinite knowledge about nature's worst medical scourges.
But like any science involved with creating or manipulating human life, studying the human embryo has become the focus of an intense international debate and has raised numerous ethical questions:
What is the moral status of a human embryo?
Is it acceptable to make an embryo in the lab only to use it for research - especially when there are at least 12,000 embryos frozen in storage and countless others that get tossed away?
How far should research embryos be allowed to develop?
At what point does an embryo become a fetus?
What kinds of research are appropriate?
Last year, the National Institutes of Health asked a panel of outside experts to wrestle with these questions. Today, its members are scheduled to release guidelines for federally funded embryo research. The report will undergo further scrutiny within the National Institutes of Health and be the subject of a public meeting in December. Harold Varmus, who heads the institutes, will then make the final decision on what areas of research are acceptable for federal funding, and which guidelines should govern the work.
Although the panel is expected to endorse human embryo research, it probably will propose certain limitations.
The panel is expected to sanction the idea of pre-implantation diagnosis, for example, so parents concerned about genetic risks can choose in vitro fertilization and learn in advance whether an embryo carries an inherited disease. But the panel is expected to deem it unacceptable to use such a technique only to determine gender.
The panel also is likely to oppose cloning, or "twinning," experiments, and research that combines human and animal tissue. But the panel may conclude that parthenogenesis - a process that uses chemicals or electrical current to stimulate the development of an egg in the absence of sperm - may be valuable in understanding egg development. These so-called parthenotes die several days after they are generated and do not develop into embryos.
Regardless of the panel's recommendations, they almost certainly will be controversial.
Expressing the view of many scientists who are among the chief advocates of the research is professor Roger A. …