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Updated: Sep 15, 2025
Morphometric Protocol for the Objective Assessment of Blastocyst Behavior During Vitrification and Warming Steps
Published on: February 28, 2019
Effect of a one-step fast warming protocol on reproductive outcomes of vitrified-warmed blastocysts
Mary Karagianni1, Achilleas Papatheodorou2, Chara Oraiopoulou1
1Embryology Department, Embryolab Fertility Clinic, Thessaloniki, Greece.
Objective:
To evaluate the effect of a one-step fast warming protocol on the survival and reproductive outcomes of vitrified-warmed blastocysts in frozen embryo transfer cycles.
Design:
Prospective cohort study.
Subjects:
This study was performed at Embryolab Fertility Clinic, in Thessaloniki, Greece, between January 2023 and June 2024 and included 1,182 embryos from 802 frozen embryo transfers. Both the study and control groups included patients with expanded blastocysts of good quality. The control group was selected to align with the study group on the basis of treatment, time period, maternal age, quality of embryos, and number of transferred embryos.
Exposure:
The fast-warming group included patients whose embryos were warmed using the one-step warming protocol: the embryos were exposed to 1M sucrose solution for 1' at 37°C and then immediately placed into culture media where laser-assisted hatching was performed. The control group included patients whose embryos were warmed using conventional protocol: 1' in 1 M, 2' in 0.5 M, 2' in 0.25 M, and 3' in washing solution at room temperature and then placed into culture media for laser-assisted hatching.
Main Outcome Measures:
The objective of this study was to compare survival, pregnancy, clinical pregnancy, ongoing pregnancy, implantation, miscarriage, biochemical pregnancy, and live birth rates between the one-step fast warming and standard warming protocols.
Results:
Pregnancy rates were comparable between the fast-warming and control groups (72.82% vs. 69.58%, relative risks [RR] = 1.12, 95% confidence intervals [CI]: 1.39). Similarly, clinical pregnancy rates showed no significant difference (56.86% vs. 57.36%, RR = 0.98, 95% CI: 0.84-1.16). Biochemical pregnancy rates were also comparable (15.61% vs. 12.46%, RR = 1.05, 95% CI: 0.96-1.14), although miscarriage rates were 6.23% in both groups. Ongoing pregnancy rates (50.62% vs. 51.12%, RR = 0.99, 95% CI: 0.86-1.14) and live birth rates (49.38% vs. 51.12%, RR = 0.96, 95% CI: 0.84-1.11) also showed no significant differences.
Conclusion:
The one-step fast-warming protocol demonstrates comparable survival and reproductive outcomes compared with the conventional multistep warming approach. Given its simplicity and efficiency, this protocol may offer an advantage in clinical settings by streamlining the warming process while maintaining embryo viability and pregnancy success rates. Further prospective studies are warranted to confirm these findings and evaluate potential benefits in larger patient cohorts.
