Developmental potential of human oocytes after slow freezing or vitrification : a randomized in vitro study based on parthenogenesis

The aim of the this study was to compare the in vitro developmental competence of parthenogenetically activated oocytes cryopreserved with slow-freezing or vitrification. Supernumerary metaphase II oocytes obtained during in vitro fertilization procedures were randomized to slow freezing or vitrification procedure. After thawing or devitrification, oocytes were parthenogenetically activated and cultured. Survival, activation, development rate, and cell number during culture were compared. The 2 groups showed no significant differences between the rates of parthenogenetic activation, development, good quality parthenotes and blastomere number on day 2 of culture. However, parthenotes from the devitrified oocytes continued cleaving till day 3 in a significantly low proportion (27% vs. 42%). On day 3, the mean number of blastomeres was also lower in vitrification group compared to slow-freezing (4.8 + 1.9 vs. 5.8 + 1.7). In conclusion, parthenogenesis highlights a reduced potential of vitrified oocytes to cleave on day 3 compared with oocytes from slow-freezing.