BLASTOCYST DEVELOPMENT IN COCULTURE - DEVELOPMENT AND MORPHOLOGICAL ASPECTS

A retrospective study was undertaken to determine if initial culture c onditions and embryo quality had an effect on subsequent blastocyst de velopment in co-culture for cryopreservation, The apparent effects of freeze-thawing on blastocysts at the ultrastructure level were also ob served, On day 3 of culture, embryos were categorized into two groups based on their morphological attributes, Results suggest that the init ial culture environment of embryos up to day 3 (5- to 8-cell stage) di d not affect the Subsequent rate of blastocyst formation in co-culture , However, the initial embryo quality had an impact on blastocyst form ation and quality, On day 5.5, 90% (60/67) of the optimal quality embr yos (six to eight blastomeres with minimal or no fragmentation on day 3) had attained the blastocyst stage, which was greater (P < 0.01) tha n the 55% (31/56) observed with the sub-optimal embryos (five to eight blastomeres with 30-50% fragmentation on day 3), Furthermore, 66% (44 /67) of embryos initially graded as optimal were suitable for cryopres ervation, which was greater (P < 0.01) than attained with embryos of l esser quality (22/56; 39%), At the ultrastructural level, the polarize d distribution of plasma membrane microvilli was retained, as was the integrity of the nuclear membrane following thawing.