These Applications Notes are offered for guidance only. They have been supplied to us by DB1 users. However, we can offer no guarantees of their effectiveness. Biotronics Ltd accepts no liabilities for losses incurred by use of these methodologies.
Comparison of frozen embryos from two different controlled rate freezers
SC Gadd and AC Gordon
Bath Assisted Conception Clinic, Royal United Hospital, Bath BA1 3NG
Objective: To compare embryo survival and clinical pregnancy rates of embryos frozen using the Cryologic and Biotronics controlled rate freezers.
Design: Retrospective study.
Materials and methods: From June 1994 to September 2000, excess embryos were cryopreserved using a Cryologic controlled rate freezer. Embryo freezing from October 2000 was carried out using a Biotronics freezing unit. The freezing protocol did not change (method of Lassalle et al. 1985) with embryos being frozen horizontally in 0.25ml straws. We analysed our embryo survival rates and clinical pregnancy rates for all frozen embryo transfer (FET) treatment cycles from January to December 2001 (n=81). A maximum of 2 frozen-thawed embryos were replaced in 93% of transfers. Data were analysed using the student’s t-test and chi-squared test.
Results:
| Cryologic | Biotronics | ||
| No. embryos thawed | 146 | 169 | |
| No. embryos 100% intact | 47 (32.2) | 91 (53.8)* | p<0.01 |
| No. embryos >50% intact (%) | 84 (57.5) | 113 (66.9) | ns |
| No. of thaw cycles | 38 | 43 | |
| No. of FETs (% of thaws) | 35 (92.1) | 42 (97.7) | ns |
| Biochemical preg (%/FET) | 6 (17.1) | 11 (26.2) | ns |
| Clinical preg (%/FET) | 5 (14.3) | 8 (19.0) | ns |
Conclusion: The number of 100% intact embryos was greater when the Biotronics controlled rate freezer was used although the clinical pregnancy rate was not significantly different.
Lassalle, B., Testart, J. and Renard, J.-P (1985) Human embryo features that influence the success of cryopreservation with the use of 1,2 propanediol. Fertil. Steril., 44, 645–651
