Intracytoplasmic sperm injection and embryo development of human oocytes cryopreserved using 1,2-propanediol

This study reports the subsequent embryo development of cryopreservedmature human oocytes following insemination or intracytoplasmicsperm injection (ICSI). Metaphase II oocytes were cryopreservedusing a slow freezingrapid thawing procedure employing the cryoprotectant1,2- propanediol. The study was conducted at two centres. Thenormal insemination of cryopreserved oocytes was undertakenin one centre, and ICSI of cryopreserved oocytes in the other.Both methods resulted in a 50% normal fertilization rate. Alow rate of abnormal fertilization was observed in the inseminatedgroup of oocytes (5%) compared with 21% for the ICSI oocytes;this was not significantly different. Embryo development wasassessed daily for 7 days. All normal fertilized cryopreservedoocytes in both groups cleaved on day 2, with a similar appearanceto in-vitro fertilization and ICSI embryos. In the normal inseminatedoocytes, there was a significant decrease in the number of embryoscleaving on day 3 (33%) compared with the development of ICSIoocytes, with a subsequent gradual reduction over days 4 and5 (22 and 11% respectively) resulting in one early blastocyston day 7 (11%). In contrast, all ICSI-generated embryos continuedto cleave on day 3, with a gradual reduction over subsequentdays (day 4, 86%; day 5, 57%; day 6, 43%; day 7, 29%). By day7, two of the blastocysts had started to hatch, resulting ina 66% hatching rate of blastocysts formed from ICSI of cryopreservedoocytes. This is the first study to show normal developmentto the hatching blastocyst stage following ICSI of cryopreservedhuman oocytes.