Efficacy and safety of a one-step warming protocol of vitrified blastocyst stage embryos

ObjectiveTo study the effect of a one-step warming technique on survival and clinical outcomes of vitrified-warmed blastocysts on a consecutive cohort of patients. DesignRetrospective consecutive cohort study. SubjectsThis study included 1402 transferred embryos from 989 unique patients that were treated in 3 clinics. ExposureThe exposure group included embryos warmed using a one-step warming protocol of 1M sucrose solution for 1 minute. The control group included embryos warmed using traditional, multi-step warming, where embryos were exposed to 1M sucrose for 1 min, followed by 3 min in 0.5M sucrose, and 10 mins in washing solutions. Main Outcome MeasuresThe goal of this study was to compare survival, clinical pregnancy (CPR) and ongoing pregnancy (OPR) rates between multi- and one-step warming techniques. Additionally, subgroup analyses by maternal age, embryo morphology, day of vitrification and mode of fertilization were also performed. ResultsSurvival rates were comparable across all comparisons. Pregnancy rates were comparable between multi-step and one-step groups (CPR: 42.6% vs 44.3%, p=0.78; OPR: 33.2 %vs 37.5%, p=0.21). Pregnancy probabilities between warming techniques were comparable between groups at any age point (32 - CPR: 43.0% vs 47.7%; OPR: 34.5% vs 39.5; p>0.05; 42 - CPR: 24.2% vs 19.3%; OPR: 13.5% vs 13.5%; p>0.05). Good quality embryos (G2) had a lower chance of pregnancy than top quality embryos (G1) overall, but pregnancy rates were similar between groups (G1 - CPR: 52.3% vs 54.6%; OPR: 46.0% vs 48.1%; p>0.05; G2 - CPR: 38.6% vs 40.0%; OPR: 27.8% vs 33%; p>0.05). Similarly, Day 6 embryos were less likely to achieve pregnancy than Day 5 embryos, but pregnancy rates were comparable between groups (D5 - CPR: 44.8% vs 46.5%; OPR: 35.3% vs 40.0%; p>0.05; D6 - CPR: 28.0% vs 31.2%; OPR: 18.3% vs 23.4%; p>0.05). Pregnancy rates between ICSI for male factor infertility and IVF were again comparable between groups (ICSI - CPR: 40.9% vs 38.3%; OPR: 33.7% vs 32.5%; IVF - CPR: 45.0% vs 48.0%; OPR: 37.3% vs 41.9%; p>0.05). ConclusionOne-step embryo warming provides similar survival and pregnancy outcomes compared to classical multi-step warming while decreasing the procedure time by more than 90%.