OBJECTIVETo investigate the effect of pre-freezing equilibration on the cryo-survival of human sperm and to optimize the protocol of direct fumigation for the freeze-thawing of human sperm.

METHODSWe collected 50 semen samples from healthy donors, each subjected to cryopreservation with 3 different methods: non-equilibration freezing (Group A), 10-min equilibration at room temperature before freezing (Group B), and 10-min equilibration at 4 degrees C before freezing (Group C). We examined all the post-thaw semen samples by computer-assisted semen analysis for the sperm motility parameters, and detected the sperm vitality and deformity index (SDI).

RESULTSThe recovery rate of progressive sperm motility was (61.88 +/- 16.94)% in Group C, remarkably higher than in A ([48.61 +/- 16.44]%) and B ([49.41 +/- 13.77]%) (P < 0.05), but with no significant difference between the latter two. And there were no significant differences in sperm vitality and SDI among the three groups.

CONCLUSIONTen-minute equilibration at 4 degrees C before freezing can evidently improve the progressive motility of sperm in addition to its advantages of easy operation and controllable experimental condition.