COCULTURED BLASTOCYST CRYOPRESERVATION - EXPERIENCE OF MORE THAN 500 TRANSFER CYCLES

Objective: To present our experience using cocultured cryopreserved an d transferred blastocysts. Design: Retrospective study of patients und ergoing transfer of cryopreserved blastocysts. Setting: Three differen t IVF centers. Patients: Four hundred sixty-seven thawed cycles from J anuary 1991 to June 1994. Main Outcome Measure: Pregnancy rate per cyc le after transfer of pre-embryos developed from thawed blastocysts. Re sults: One thousand two hundred thirty-nine blastocysts were thawed. O f these, 1,033 (83%) survived thawing and were transferred. Five hundr ed sixty-three thawed cycles resulted in 516 (92%) receiving intrauter ine transfer. One hundred twelve clinical pregnancies were established , resulting in a 21.7% pregnancy per transfer with a 19% ongoing rate. The implantation rate of 13.4% results from 138 implanted pre-embryos . There was a higher PR in the programmed cycle (79/302; 26.2%) compar ed with the natural cycle (6/47; 13%). Conclusions: Freezing at the bl astocyst stage is a proven and reliable method in IVF technology. Alth ough there may be fewer pre-embryos, their ability to implant appears to approach the potential of a fresh transfer.