A third of Americans find stem cell research morally offensive -- but how many have unwittingly contributed to it by giving up eggs?

Many U.S. fertility clinics don't tell egg donors that embryos made from their eggs may end up being used in stem cell research, according to a new government survey. That's despite widespread opposition to such research, which is considered morally offensive by a third of Americans, researchers write in the journal Fertility and Sterility.

They found that among 100 fertility clinics, two said they didn't have a consent form for women donating eggs. Of the 66 clinics that sent in a consent form and said they used excess embryos for research, just 20 told women about that. And only three of 38 clinics that used some embryos for stem cell research in particular disclosed that to donors.

"Clearly it is important for women to know where their eggs are going. But we don't know from this survey, are women upset by this?"

"The survey shows that only a minority of IVF (in vitro fertilization) clinics mention to egg donors who are donating for the sake of treatment (as opposed to research) that resultant embryos might ultimately be used in research," said study co-author Gerald Owen Schaefer of the National Institutes of Health in Bethesda, Maryland. "An even smaller minority mention stem cell research explicitly."

"Since possible research use of embryos, especially for stem cell research, may be material information affecting some women's decision about donation, egg donors should be so informed," he and his colleagues wrote in the paper.

Some women have eggs taken out as part of their own fertility treatment, while others receive handsome payments -- often several thousand dollars -- to donate an egg.

"We recommend that all IVF clinics that provide some embryos for research inform egg donors about the possibility of such research (including stem cell research, which is particularly controversial)," Schaefer told Reuters Health by email. That agrees with several organizations such as the National Academy of Sciences and the International Society for Stem Cell Research.

Bioethicists not involved in the new study questioned whether disclosing that surplus embryos might be used for research would have an effect on women's decision to donate. "I think it's unlikely that this would have an impact on women who are engaged in commercial egg donation," said Dr. Steven Miles, a professor of bioethics at the University of Minnesota in Minneapolis. "Whether it should be disclosed is another issue -- in general, disclosure is a good thing."

Raymond De Vries, a social scientist and a professor of bioethics at the University of Michigan Medical School in Ann Arbor, said the survey left crucial questions unanswered. "Clearly it is important for women to know where their eggs are going. But we don't know from this survey, are women upset by this?" he told Reuters Health. "What is missing is, these women who donate eggs, what do you know about them?"

De Vries said there are examples of ads luring in potential donors with compensations upward of $10,000, although harvesting an egg is not a straightforward procedure. "Getting an egg out of a woman is not like going to the chicken coop and getting an egg," he said. "It is not a completely risk-free endeavor." Yet, there is no federal regulation of IVF clinics in the U.S., according to De Vries. "It's cowboy land out there," he said.

Image: Monkey Business Images/Shutterstock.