One of the major obstacles of organ transplantation is that the organ has to be transplanted within a few hours of being removed from the donor. Researchers in Canada reported in 2002 that they successfully transplanted rat ovaries that had been frozen in liquid nitrogen. Previous attempts at freezing organs have failed, mainly because chemicals used in the freezing process damaged delicate blood vessels. This problem seems to have been overcome by infusing the organs in a protective fluid, slowly cooling them and then storing them in liquid nitrogen. Although study results show that the technique is not perfect and needs refining, as just over 50% of the seven transplants carried out with frozen ovaries were successful, compared with 100% of those using "fresh" organs.
In 1998 the number of organ donors in the US increased significantly for the first time in years. As a result, approximately 600 more organ transplants were performed than in 1997, though demand for organs still drastically outweighs supply. The increase was fueled by a new rule under which hospitals must report all deaths to the organizations that approach families to enlist donors.