Variable motility recovery of spermatozoa following freeze preservation.

Semen from a random group of potentially fertile men and a small number of donors who had established an artificial insemination pregnancy was mixed with a cryoprotective agent and frozen by two different methods. After 1 week under liquid nitrogen (-196 degrees C), all samples were thawed and their motilities determined. The post-thaw motilities were compared with the prefreeze motilities. The mean motility recovery rate in the group of semen samples with high counts was better than that in the group with counts in the low-normal range. The recovery rate with the slow-freeze method was slightly higher than that with the quick-freeze technique. However, the wide range of post-thaw motility among the random donors (0 to 60%) and the donors of proven fertility (15 to 45%) demonstrated that prefreeze motility and/or paternity history was no guarantee of good motility recovery following freezing. At a time when semen banking is being contemplated for "fertility insurance" prior to vasectomy, it is apparent that a trial freeze is necessary before recommending freeze-preservation of his semen to the man contemplating permanent surgical sterilization.