There are almost half-million frozen embryos stored in fertility clinic freezers across the country. Most couples attempting to have children through in-vitro fertilization keep their unused frozen embryos indefinitely.

Eventually, most of those embryos are destroyed.

The University of Minnesota is offering couples choice – to donate their unused embryos for research on stem cells.

After the clinic completes an agreement with the university, it will be one of two IVF clinics in the state giving patients the chance to donate embryos to university stem-cell researchers. The other is the university’s Reproductive Medicine Center.

A Roseville company, ReproTech, which provides long-term storage for embryos, also offers customers the chance to donate embryos to science, including stem-cell research.

The university has donation agreements with six clinics across the country, said Meri Firpo, an embryonic stem-cell researcher.

So far, they have provided her lab with more than 20 embryos for research.

Academic institutions across the country are developing guidelines that provide a legal and ethical basis for stem-cell research donation, said Jeff Kahn, director of the Center for Bioethics at the University of Minnesota.

The university’s new rules for such embryo donations require that they be anonymous, and that patients cannot choose how their embryos will be used, Firpo said. People can donate embryos only through their IVF clinic. There can be no financial return to donors or clinics for embryos.