Effect of the length of time that donated embryos are frozen on pregnancy outcome.

Purpose: To determine if the longer length of time that embryos donated to an anonymous couple have been frozen has a negative effect of subsequent successful pregnancy following thawing and transfer to the recipients.

Methods: Retrospective determination of pregnancy rates according to the length of cryopreservation time has on pregnancy outcome following transfer of embryos designated for donation.

Results: Longer time of freezing did not adversely affect subsequent pregnancy rates following frozen embryo transfer.

Conclusions: Donated embryos frozen for over five years (the time when some countries demand that the embryos be discarded) contributed to one-fourth of the donor embryo pool and one-third of the live deliveries.