TRANSFER OF CRYOPRESERVED EMBRYOS IMPROVED PREGNANCY RATES IN PATIENTS WITH DAMAGE TO THE FUNCTIONAL INTEGRITY OF THE SPERM MEMBRANE AS MEASURED BY THE HYPOOSMOTIC SWELLING TEST

Objective: To compare the pregnancy rates (PRs) after transfer of cryo preserved embryos in patients who have damage to the functional integr ity of the sperm membrane as measured by the hypo-osmotic swelling tes t to those without this defect. Design: Prospective clinical study. Se tting: University-associated IVF center. Patients: Fifty-four patients enrolled in a matched prospective study to evaluate the effects of lo w HOS scores (<50%) on PRs after IVF-ET were followed to determine the PR after transfer of cryopreserved embryos. Main Outcome Measure: Cli nical PRs and implantation rates. Results: Fourteen patients with low hypo-osmotic swelling test scores underwent 21 frozen ET cycles, achie ved four clinical pregnancies for a PR per cycle of 19.0% and an impla ntation rate of 7.1%. Twelve patients with normal hypo-osmotic swellin g test scores underwent 21 frozen ET cycles, achieved five pregnancies for a clinical PR per cycle of 23.8% and an implantation rate of 9.3% . Conclusion: Previous studies have demonstrated an adverse effect of low hypo-osmotic swelling test scores on PRs after IVF-ET despite norm al fertilization. This adverse effect was not found in the transfer of cryopreserved embryos from males with low hypo-osmotic swelling test scores. Further investigation is required to determine how cryopreserv ation improves the chances of implantation of these embryos.