Vitrification of human oocytes following minimal exposure to cryoprotectants; initial studies on fertilization and...

Investigations were made into the low temperature preservation of pre-ovulatory human oocytes by vitrification using a method of brief exposure of the oocytes to the vitrification solution at room temperature. Assessments of morphological survival, fertilization and embryonic development were recorded. All those oocytes exposed to the vitrification solution alone were morphologically normal and 86% of them were fertilized after incubation with spermatozoa. All the fertilized ova (86%) underwent cell division. Following cooling to -196 degrees C, morphological survival (65%) and fertilization (45%) rates remained high. However, in all vitrified oocytes, embryonic cell division and further development were inhibited. From our study it appears that fresh human oocytes can be vitrified using only brief exposure to cryoprotective agents and survive to undergo fertilization. However, progress remains to be made in achieving further embryonic development.