The Effects of Two Different Freezing Method on Survival and Development of Pronuclear Stage Human Embryos

چکیده مقاله

Introduction: Nowadays, cryopreservation of human embryos has become a required part of IVF programs. The purpose of this study was to compare the recovery, survival, cleavage and blastocyst development rate of pronuclear stage human embryos, after slow freezing and vitrification methods. Material and Methods: Human 2PN stage embryos were divided randomly into four groups. In the 1M (control) group 29 embryos included without any exposure. In the sham or 2nd group 15 embryos were considered to survey for cryoprotectant toxicity. Embryos in the 3rd and 4th group freezed by vitrification and slow freezing methods respectively. Embryos in 3rd group (n=36), were vitrified using a new vitrification solution. Survived embryos were cultured, incubated and evaluated for 5 days post-thawing. In 4th group, 2PN embryos (n=41) were freezed in propanediol (PROH) and sucrose 16-18 hours posICSI using a programmed freezing instrument (Planner Series III) and plunged into liquid nitrogen. Results: Our data showed that survival rate in 1M (control) group was significantly (P<0.05) more than other groups, meanwhile cleavage rate in the control group is significantly more than only slow freezing (4th) group (96.55% vs 76=19%). The blastocyst formation rates in the 3rd and 4th groups are significantly lower than control group (59.09% and 42.85% vs 65.51%). Comparison of cleavage and blastocyst formation rate showed a significant difference between 3rd and 4th groups. The survival rate has a significant difference between groups (100%, 93.33%, 70.96% and 65.62% respectively) (P<0.05). Discussion: The pronuclear stage embryos from ICSI could choosen for cryopreservation because the developmental capacity of the embryos, after thawing, can easily be ascertained and the predominance of study has shown that human embryos survive and implant at higher rates, when frozen in 2PN. Conclusion: Both procedures had nearly similar effect on 2PN human embryos, but the vitrification method is better because of its simplicity, quickness and cost effectiveness