COMPARISON OF CRYOPRESERVATION OF SUPERNUMERARY PRONUCLEAR HUMAN OOCYTES OBTAINED AFTER INTRACYTOPLASMIC SPERM INJECTION (ICSI) AND AFTER CONVENTIONAL IN-VITRO FERTILIZATION

A comparison was made of pronuclear stage human oocytes obtained eithe r after classical in-vitro fertilization (IVF) or after intracytoplasm ic sperm injection (ICSI), After ICSI or IVF, three fertilized oocytes from each patient were kept in culture for a further 24 h before embr yo transfer, The surplus oocytes were cryopreserved using the 'open fr eezing system' and 1,2-propanediol and sucrose as cryoprotectants, A c ohort of 817 and 1626 oocytes in pronuclear stage were frozen after IV F and ICSI respectively, Of these, 333 and 744 zygotes have been thawe d, of which 78 and 76.5% were morphologically intact zygotes after IVF and ICSI respectively, From the 204 (ICSI) and 89 (IVF) zygote transf ers performed, 34 (17%) and 18 (20%) pregnancies were established, Bot h groups showed a similar abortion rate of similar to 20%. It is concl uded that pronuclear stage oocytes resulting from ICSI can be successf ully frozen/thawed and the survival and pregnancy rates achieved are c omparable to those for zygotes obtained after IVF.