Clinical experience with ultrarapid cryopreservation of human embryos resulting from intracytoplasmic sperm injection

A total of 41 patients requested thawing of supernumerary embryos in an intracytoplasmic sperm injection (ICSI) programme. Mean patient age was 30.8 +/- 3.8 years. Embryo freezing by the ultrarapid method was performed at room temperature in 3 mol/l DMSO and 0.25 mol/l sucrose, Total freezing time was 2.5 min including filling of the straw In the thawing process, the embryos were removed from liquid N-2, left at room temperature for 30 s, immersed for 40 s at 30 degrees C, and then successively transferred at room temperature for 10 min to each of three sucrose solutions of decreasing concentration. The embryos were kept in culture and only those that presented cleavage after 24 h were transferred. Embryos from 42 cycles were thawed and a total of 24 transfers was performed. The mean number of thawed embryos was 5.0 +/- 3.2 per cycle and the mean number of transferred embryos was 2.83 +/- 1.3. The clinical pregnancy rate per cycle obtained after the thawing process was 16.6%. The clinical pregnancy rate per transfer was 29.2% and the implantation rate was 13.2%, The abortion rate was 14.3%. Six deliveries hare been performed, with the birth of seven infants.