ABSTRACT
OBJECTIVE: To evaluate the clinical role of blastocyst freezing and thawing after prolonged culturing in sequential media. DESIGN: Retrospective analysis of 293 blastocyst freeze-thawing cycles. SETTING: University hospital infertility unit. PATIENT(S): Nonselected couples undergoing IVF. INTERVENTION(S): Blastocysts were frozen and thawed by a modified method. MAIN OUTCOME MEASURES: Blastocyst recovery after freeze-thawing and pregnancy rates after the transfer. Evaluation of the effect of the number of transferred blastocysts, the method of IVF, and of the woman's age on the results achieved by frozen-thawed blastocysts. RESULT(S): Frozen-thawed blastocysts provided a 29.5% clinical pregnancy rate per transfer. After the transfer of three blastocysts the pregnancy rate was 42.0%, and after the transfer of one or two blastocysts it was approximately the same (25.0% and 28.0%, respectively). The method of IVF did not affect pregnancy rates, but the increasing age of the woman did. Pregnancies were characterized by a low abortion rate (8.0%) regardless of the age of the woman. CONCLUSION(S): A modified method for blastocyst freeze-thawing provides good clinical results. It offers the possibility for a single-thawed blastocyst transfer and represents a good alternative for older women because of its lower risk of spontaneous abortion.
