A modified embryo cryopreservation method increases post-thaw survival with a concomitant increase in implantation.

OBJECTIVE To achieve maximum post-thaw survival of frozen embryos. DESIGN Historical controlled study. SETTING Hospital-based fertility center. PATIENT(S) One hundred forty-five patients whose embryos were frozen and thawed according to the standard method, and 56 patients whose embryos were frozen and thawed according to a modified method. INTERVENTION(S) Modifications were made to the various steps of cryopreservation: freezing and thawing solutions, loading of embryos into the straws, and warming rates. MAIN OUTCOME MEASURE(S) Post-thaw survival, implantation, and pregnancy rates. RESULT(S) With the modified method, 138 (93%) of the 149 embryos thawed for 56 patients survived freezing, and 79.8% had all their blastomeres intact, which is almost double the result obtained (41.8%) for patients whose embryos were thawed with the standard method. The implantation and pregnancy rates were also significantly higher with the modified method compared with the standard method. CONCLUSION(S) Greater post-thaw embryo survival was achieved, with a concomitant increase in implantation and pregnancy rates, by modifying the various steps in the standard cryopreservation methodology. This has important implications in IVF practice.