Choosing the optimal blastocyst by morphology score versus developmental rate in frozen-thawed embryo transfer cycles

Abstract

The aim of this study was to provide guidance for better management in the selection of blastocyst to warm in frozen-thawed embryo transfer (FET) cycles. A retrospective cohort follow-up study was conducted that included single autologous frozen blastocyst transfer cycles performed in our Reproductive Medicine Unit from January 2009 to December 2016. The live birth rate (LBR), clinical pregnancy rate (cPR) were increased as blastocyst morphology scores increased, but the miscarriage rate decreased in all groups. In the high-score groups, there were no differences in LBR between D5 and D6, while in the low-score groups, LBR was significantly higher in D5 compared to the D6. With respect to neonatal outcome, there were no differences in all the groups. After binary logistic regression analysis, it was seen that patients’ age, thawed cycles, pre-frozen morphology score and developmental rate were independently associated with LBR. These results suggest that for high-scoring blastocyst, the pre-frozen morphological score should be given priority while for low-scoring blastocysts, the developmental rate should be given priority when thawing in FET cycles.

Keywords:

• Frozen-thawed embryo transfer
• delayed blastulation
• live birth rate
• morphology score
• development rate

Acknowledgements

The authors would like to thank the clinicians, clinical embryologists, laboratory technologists and nurses for their support to this study. The authors would also like to thank Dr. Dev Sooranna, Imperial College London, for editing the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).