Objective: To present our experience using cocultured cryopreserved and transferred blastocysts.
Design: Retrospective study of patients undergoing transfer of cryopreserved blastocysts.
Setting: Three different IVF centers.
Patients: Four hundred sixty-seven thawed cycles from January 1991 to June 1994.
Main outcome measure: Pregnancy rate per cycle after transfer of pre-embryos developed from thawed blastocysts.
Results: One thousand two hundred thirty-nine blastocysts were thawed. Of these, 1,033 (83%) survived thawing and were transferred. Five hundred sixty-three thawed cycles resulted in 516 (92%) receiving intrauterine 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%) compared with the natural cycle (6/47;13%).
Conclusions: Freezing at the blastocyst stage is a proven and reliable method in IVF technology. Although there may be fewer pre-embryos, their ability to implant appears to approach the potential of a fresh transfer.