In 2001, gestational carriers, or surrogates, were involved in 0.7% of ART cycles using fresh nondonor embryos in 2001 (571 cycles).Donor eggs or embryos were used in slightly more than 11% of all ART cycles carried out in 2001 (12,018 cycles). Few women younger than age 39 used donor eggs; however, the percentage of cycles carried out with donor eggs increased sharply starting at age 39. About 76% of all ART cycles among women older than age 45 used donor eggs.In 2001, 89% of reporting clinics offered donor-egg programs, 58% offered donor-embryo programs, and 69% offered gestational carriers.Frozen embryos Cryopreservation was offered by 98% of reporting clinics in 2000.There are an estimated 400,000 frozen embryos in fertility centers in the United States.Almost 90% of frozen embryos are intended to be used by the couples from whose gametes they were derived-to use if the fresh cycle of treatment does not work or if they want to have another child at a later date. Of the approximately 4% of frozen embryos available for donation, it is estimated that 11,000 are destined for research and 9,000 for other couples. Approximately 9,000 are currently destined to be thawed without use. i ''Abandoned'' embryos-which are unclaimed after a set period of years and after diligent efforts have been made to contact the couple involved-are not used for research or donation.