Effects of different open cryo-carriers on embryo survival and clinical outcome in frozen embryo transfer cycle patients

The purpose of this study was to compare the efficacy of different open cryo-carriers: the CryoloopTM, CryotopTM, and CryoleafTM, in embryo survival and clinical outcome in patients with frozen embryo transfer (FET) cycle. We analyzed the embryo survival rate and clinical outcome in 325 patients of 348 FET cycles vitrified with the CryoloopTM (160 cycles), CryotopTM (105 cycles), or CryoleafTM (83 cycles). No significant differences were observed in embryo survival rate (98.8% vs. 100% vs. 97.7%, p > 0.05), HCG positive rate (58.8% vs. 63.8% vs. 57.8%, p > 0.05), biochemical pregnancy rate (6.9% vs. 11.4% vs. 9.6%, p > 0.05), or implantation rate (33.2% vs. 37.4% vs. 34.1%, p > 0.05) in the three groups respectively. The early abortion rate of the CryoloopTM group was significantly higher than that of the CryotopTM and CryoleafTM group (27.1% vs. 3.6% and 7.5%, p < 0.05). At the same time, the average female age of the CryoloopTM group was significantly older by 1 year than that of the CryotopTM and CryoleafTM group (33.29 ± 4.71 years vs. 31.96 ± 4.27 years and 31.1 ± 4.28 years, p < 0.05). There was no significant difference in take home baby rate (38.1% vs. 46.7% vs. 43.4, p > 0.05) or birth weight among the groups (2893.5 ± 780.8 g vs. 2778.4 ± 710.0 g vs. 2724.5 ± 838.8 g, p > 0.05). No case of neonatal malformation was observed in the present study. Overall, CryotopTM and CryoleafTM were effective for embryo vitrification at both the cleavage and blastocyst stage according to the results of clinical outcome and infant characteristics. However, CryoloopTM led to a decreased positive HCG rate and increased early abortion rate, heightened at the cleavage stage.

Abbreviations: LN₂: liquid nitrogen; CPA: cryoprotectant; ART: assisted reproductive technology; IVF: in vitro fertilization; ICSI: intracytoplasmic sperm injection; BMI: body mass index; FSH: follicular stimulation hormone; COH: controlled ovarian hyperstimulation; FET: frozen embryo transfer; mm: millimeter; HCG: human chorionic gonadotropin; RCT: randomized clinical trial; NC: natural cycle; AC: artificial cycle; EM: equilibration medium; DMSO: dimethyl sulphoxide; EG: ethylene glycol; VM: vitrification medium; WM: warming medium