D H Edgar1, H Jericho, H Bourne, J C McBain. 1. Reproductive Biology Unit, Royal Women's Hospital, 132 Grattan Street, Carlton, Victoria 3053, Australia. david@mivf.com.au
Abstract
PURPOSE: To determine whether the relatively low implantation rate of cryopreserved Day 2 embryos with only 2 blastomeres can be increased as a consequence of increasing their blastomere content by extending the prefreeze culture time. METHODS: Of a total of 3480 Day 2 embryos studied, 1921 (55.2%) had reached the 4-cell stage by 40 h postinsemination (FAST) and were transferred or cryopreserved. The remaining embryos that underwent subsequent cell division by 46 h (INTERMEDIATE; 18.3% of total) or 66 h (SLOW; 20.3% of total) were also cryopreserved whereas the 6.2% that remained arrested at 66 h were discarded. Thawed embryos from each category were assessed for survival, post-thaw cleavage, and implantation. RESULTS: The proportion of thawed embryos that survived, the proportion of surviving embryos that underwent post-thaw cleavage, and the implantation rate of transferred embryos were all reduced in the slower growing cryopreserved embryos. CONCLUSIONS: The growth rate, and not the number of blastomeres per se, is a critical factor in predicting the developmental potential of cryopreserved embryos.
PURPOSE: To determine whether the relatively low implantation rate of cryopreserved Day 2 embryos with only 2 blastomeres can be increased as a consequence of increasing their blastomere content by extending the prefreeze culture time. METHODS: Of a total of 3480 Day 2 embryos studied, 1921 (55.2%) had reached the 4-cell stage by 40 h postinsemination (FAST) and were transferred or cryopreserved. The remaining embryos that underwent subsequent cell division by 46 h (INTERMEDIATE; 18.3% of total) or 66 h (SLOW; 20.3% of total) were also cryopreserved whereas the 6.2% that remained arrested at 66 h were discarded. Thawed embryos from each category were assessed for survival, post-thaw cleavage, and implantation. RESULTS: The proportion of thawed embryos that survived, the proportion of surviving embryos that underwent post-thaw cleavage, and the implantation rate of transferred embryos were all reduced in the slower growing cryopreserved embryos. CONCLUSIONS: The growth rate, and not the number of blastomeres per se, is a critical factor in predicting the developmental potential of cryopreserved embryos.
Authors: J Mandelbaum; J Belaïsch-Allart; A M Junca; J M Antoine; M Plachot; S Alvarez; M O Alnot; J Salat-Baroux Journal: Hum Reprod Date: 1998-06 Impact factor: 6.918