3. A randomized controlled study of human Day 3 embryo cryopreservation by slow freezing or vitrification: vitrification is associated with higher survival, metabolism and blastocyst formation.
BACKGROUND: The aim of this study was to compare two methods of cryopreservation for the cleavage-stage human embryo: slow freezing and vitrification. METHODS: A total of 466 Day 3 embryos, donated with consent, underwent cryopreservation by either slow freezing in straws or vitrification using the cryoloop. The vitrification procedure did not include dimethyl sulfoxide, but rather employed ethylene glycol and 1,2-propanediol as the cryoprotectants. Survival, embryonic metabolism and subsequent development to the blastocyst were used to determine the efficacy of the two procedures. RESULTS: Significantly, more embryos survived the vitrification procedure (222/234, 94.8%) than slow freezing (206/232, 88.7%; P < 0.05). Consistent with this observation, pyruvate uptake was significantly greater in the vitrification group, reflecting a higher metabolic rate. Development to the blastocyst was also higher following vitrification (134/222, 60.3%) than following freezing (106/206, 49.5%; P < 0.05). In a separate cohort of 73 patients who had their supernumerary embryos cyropreserved with vitrification, the resulting implantation rate and clinical pregnancy rate were 30 and 49%, respectively. CONCLUSIONS: Analysis of metabolism revealed that vitrification had less impact on the metabolic rate of the embryo than freezing, which was reflected in higher survival rate and subsequent development in vitro. Excellent pregnancy outcomes followed the warming and transfer of vitrified cleavage-stage embryos. These data provide further evidence that vitrification imparts less trauma to cells and is, therefore, a more effective means of cryopreserving the human embryo than conventional slow freezing. Clinicaltrials.gov identifier: NCT00608010.
Reference
Balaban B, Urman B, Ata B, Isiklar A, Larman MG, Hamilton R, Gardner DK.
A randomized controlled study of human Day 3 embryo cryopreservation by slow freezing or vitrification: vitrification is associated with higher survival, metabolism and blastocyst formation.
Hum Reprod. 2008 Sep;23(9):1976-82. Epub 2008 Jun 10.
4. From oocyte to baby: a clinical evaluation of the biological efficiency of in vitro fertilization.
OBJECTIVE: To assess the real biological efficiency of assisted reproduction technology (ART) cycles by using a new metric called oocyte to baby rate, where live babies born (LBB) are reported in relation to the number of oocytes retrieved and used. DESIGN: Retrospective analysis of clinical and embryological database. SETTING: University center. PATIENT(S): Patient’s cycles (n = 572) divided by age (<35, 35 to 37, 38 to 40, 41 to 42, >42 years) and by oocyte donors. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Total number of oocytes collected, the number of embryos transferable (fresh and frozen) and corresponding oocyte to LBB rates. In patients with remaining frozen embryos, the final LBB was estimated according to our reported rates. RESULT(S): A total of 572 oocyte retrievals yielded 7213 oocytes. The total number of transferred and frozen embryos was 2252 (a utilization rate of 31.2%). The LBB from fresh embryo transfers was 262 with an additional 64 LBB expected from frozen embryos. The overall oocyte to LBB rate was 4.6% (326 babies born). When analyzed by groups, the oocyte to baby rate was best in donor oocyte cycles (6.8%), and declined to 1% for patients >40. There was no increase in oocyte to LBB if >15 oocytes were obtained. CONCLUSION(S): During ART cycles, only approximately 5% of fresh oocytes produce a baby. The time has come to investigate new methods of oocyte viability assessment and consider changing current ART practice to recruit fewer oocytes.
Reference
Patrizio P, Sakkas D.
From oocyte to baby: a clinical evaluation of the biological efficiency of in vitro fertilization. Fertil Steril. 2009 Apr;91(4):1061-6. Epub 2008 Mar 5.
