Prognostic value of morphologic characteristics of cryopreserved embryos: a study using videocinematography

Fifty embryos, previously frozen at the zygote or 2- to 4-cell stage, were studied. Observers, who were unaware of the occurrence of pregnancy, assessed the morphologic features of these embryos by retrospectively analyzing videocinematographic recordings that were made shortly before replacement. Seven of 26 zygotes and 4 of 24 cleaved embryos implanted, with the incidence of implantation being analyzed in relation to 12 morphologic characteristics. Smooth surface of the blastomere's membranes was a statistically significant predictor of implantation for frozen-cleaved embryos, and variable zona pellucida thickness was the only parameter with predictive value for frozen zygotes. A highly significant difference was found between the implanting capacity of previously frozen-cleaved embryos and the number of abnormal morphologic characteristics. Three quarters of the thawed embryos had at least two abnormal characteristics, indicating that cryodamage was high. Major advantages of videocinematography are the absence of time constraints associated with observing live embryos, the ability to observe new morphologic parameters by freeze-frame and slow motion, and the permanent storage of embryonic data for quality control evaluation.