Received August 30, 2002
Accepted September 12, 2002

Objective:The objective of this study was to evaluate and report the efficacy of freezing ali embryos in patients with OHSS risk. Study Design:A total of 36patients who were submitted to an ovarian stimulation cycle for ICSI and presented an ovarian diameter=50cm3 at the day of human chorionic gonadotrophin(hCG) ad ministration and/or were collected=25 inmature and mature oocytes were considerate as patients with OHS risk and had ali their embryos cryopreserved.Cryopreservation of ali cleavage stage embryos was carried out using slow method with 1.2propanediol protocol in an CL 863 Cryologic apparatus. Following the thawing process the embryos were inspected separately in terms of survival(at least one blastomere intact) and c1eavage(after 24 hours the division of at least one of the blastomere).A total of 45 tranfers were carried out in two hormonal schemes i.e natural cycle and substitutive cycle. Results: AlI patients (36) had no severe OHSS after oocyte retrieval and did not require hospitalization. The mean age of the patients was 30.2±4.6 years. The mean of retrieved oocytes was 26.1±9.1 and 481 embryos were frozen. A total of 57thawed cycles were perform ed and 85.7% of embryos presented at least one blastomere intacto The frequency of embryo cleavage was 81.1%±24.4 and the mean number of embryo cleavage transferred was 2.6±0.8.The clinical pregnancy rate per thawing cycle was 43.8%(25/57).The c1inical pregnancy rate per embryo transfer was 45.4%(25/55).The rate of embryo implantation was 22.5%. Conclusion:This study demonstrates that to cryopreserve all embryos is an effi cacy proceeding to prevent OHS in high risk patient.