Use of fluorescence in situ hybridization to assess the chromosomal statusof embryos obtained from cryopreserved oocytes

Objective: To analyze the chromosomal status of human embryos obtained from frozen-thawed oocytes. Design: Fluorescence in situ hybridization analysis of embryos obtained aft er oocyte cryopreservation. Setting: Department of Obstetrics and Gynecology at the University of Perug ia, Italy, and the Institute Valenciano de Infertilidad, Spain. Patient(s): Oocyte donors (n = 43). Fertilization, development, and chromos omal status of the embryos were compared with a control group (n = 18) of p atients undergoing preimplantation genetic diagnosis for sex chromosome-lin ked diseases. Intervention(s): Collection of oocytes after conventional ovarian stimulati on and cryopreservation using propanediol as the cryoprotectant and a slow freezing procedure. Microinjection of surviving metaphase II oocytes and ev aluation of fertilization and embryo development up to blastocyst stage. Ch romosomal analysis after embryo biopsy. Main Outcome Measure(s): Survival, fertilization, and blastocyst rates. Emb ryo chromosomal analysis employing specific probes for chromosomes 13,18,21 , X and Y. Result(s): The overall survival rate was 59.4%. There was no difference bet ween cryopreservation and control groups in fertilization rates (76.5% vs. 90.5%) or blastocyst development (29.6% vs. 35%). The percentage of blastoc ysts from the original number of cryopreserved oocytes was only 5.6%, compa rable to the 5.9% obtained in the control group. The percentage of embryos with abnormal number of chromosomes in the cryopreservation group (28.6%) w as comparable to the 26% observed in the controls. Conclusion(s): Fertilization and cleavage rates after oocyte freezing are a cceptable, Survival is, however, still poor, leading to overall results tha t make the technique clinically inefficient. There is no increase in the ra te of chromosomal abnormalities, indicating that the technique is, neverthe less, safe enough to be further explored and improved. (Fertil Steril((R)) 2001;75:354-60. (C)2001 by American Society for Reproductive Medicine.).