Standardization of Post-Vitrification Human Blastocyst Expansion as a Tool for Implantation Prediction

Anat Hershko-Klement*, Shaul Raviv, Luba Nemerovsky, Tal Rom, Ayelet Itskovich, Danit Bakhshi, Adrian Shulman, Yehudith Ghetler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The increased use of vitrified blastocysts has encouraged the development of various criteria for selecting the embryo most likely to implant. Post-thaw assessment methods and timetables vary among investigators. We investigated the predictive value of well-defined measurements of human blastocyst re-expansion, following a fixed incubation period. Post-thaw measurements were taken exactly at 0 and 120 ± 15 min. Minimum and maximum cross-sectional axes were measured. Three groups were defined: Group 1: embryos that continued to shrink by 10 µm or more; group 2: embryos that ranged from −9 to +9 µm; and group 3: re-expansion of 10 µm or more. Patient and morphokinetic data were collected and integrated into the analysis. A total of 115 cases were included. The clinical pregnancy rate for group 1 was 18.9%; group 2, 27%; and group 3, 51.2% (p = 0.007). Pre-thaw morphologic grading and morphokinetic scores of the study groups did not reveal differences. p-values were 0.17 for the pre-thaw morphologic score, 0.54 for KID3, and 0.37 for KID5. The patients’ demographic and clinical data were similar. The clinical pregnancy rate correlated with the degree of thawed blastocyst re-expansion measured 2 h after incubation. This standardized measure is suggested as a tool to predict the potential of treatment success before embryo transfer.

Original languageEnglish
Article number2673
JournalJournal of Clinical Medicine
Issue number9
StatePublished - 1 May 2022


  • blastocyst
  • expansion
  • in vitro fertilization
  • pregnancy rate
  • vitrification


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