Comparison of clinical outcome after cryopreservation of embryos obtained from intracytoplasmic sperm injection and in-vitro fertilization.

The impact of intracytoplasmic sperm injection (ICSI) on cryopreserved zygotes and embryos was evaluated by comparing embryo survival and implantation between embryos derived from ICSI and those derived from standard insemination procedures. The study included patients whose excess zygotes and embryos were cryopreserved between September 1993 and December 1994 and who subsequently underwent a frozen embryo transfer. Embryo survival, clinical pregnancy rates per transfer and pregnancy outcome were compared. Three hundred and thirty eight cryopreservation cycles, during which 1471 embryos were cryopreserved, were included in this study. Of those, 961 were derived from oocytes fertilized by insemination in vitro and 510 were derived from oocytes fertilized by ICSI. A total of 690 of the embryos (451 in the insemination group and 239 in the ICSI group) have since undergone a thaw cycle. The embryo survival rates were similar between the two groups (70.5 and 73.2%, insemination and ICSI respectively) and were not significantly affected by the stage at cryopreservation. There was no significant difference in pregnancy rates per transfer (31.8 and 32.3%), the preclinical pregnancy loss rate (16.7 and 23.8%), or the clinical miscarriage rate (16.7 and 23.8%) between the insemination and the ICSI groups respectively. It is concluded that ICSI does not have an adverse impact on the survival and successful implantation of cryopreserved and thawed embryos.