Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Zoology

Cryogenic preservation of the oocytes gains more importance nowadays in the programs of the in vitro fertilization (IVF). The study aims to help extending the applications of oocytes cryopreservation into the clinical practice of assisted reproduction programs. Using the vitrification method applied on 676 human oocytes divided into four groups based on their maturation stage, presence of corona cells and the time to start oocytes cryopreservation. Group (A) includes 177 MII oocytes, fully denuded and vitrified 3-5 hours after pick up, Group (B) includes 194 GV/MI oocytes fully denuded and vitrified 3-5 hours after pick up, Group (C) contains 103 oocytes vitrified 24 hours from retrieval at the MII stage and fully denuded and Group (D) contains 202 oocytes vitrified with the corona cells at the MII stage 3-5 hours after pick up. Survivability is determined one hour after thawing then the survived oocytes undergo ICSI procedure. In group (A), after thawing 161 oocytes (91%) survived, 111 oocytes (69%) fertilized, and only 38 oocytes (34%) completed their development into blastocysts. In group (B), 167 oocytes (86%) survived then 60 oocytes (36%) matured to MII, and 40 oocytes (67 %) fertilized, then 11 embryos (28%) reached the blastocyst stage. In group C, 67 oocytes survived (65%), 44 oocytes fertilized (66%) and 8 embryos (18%) reached blastocyst stage. In Group D, 188 oocytes survived (93%), 126 oocytes got fertilized (67%) and 39 embryos reached the blastocyst stage (31%). The vitrification method in the cryopreservation of the oocytes is very successful in preserving viability and fertilization .The presence or removal of the corona cells before vitrification didn't affect the results. Delaying vitrification 24 hours significantly lowered the results

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