Background: The high fertilization failure after IVF treatment cycles could be related to chromosomal abnormalities. This study was carried out to assess the frequency of chromosomal abnormality on human oocytes lacking signs of fertilization 18-20 h after insemination . Materials and Methods: On day one, 18-20 h after insemination (IVF), fertilization wasconfirmed when two pronuclei (normal IVF) or more pronuclei (poly pronucleus FR) were present.Chromosomal analysis of unfertilized oocytes
was carried out within 20-24 h of collection. All oocyte did not sign of pronuclei were collected from total fertilization failure, TFF (FR=0) or partialfertilization failure, PFF (FR=10-90%). Chromosomal preparation was carried out as described byTarkowski’s techniques. The average of finding between two groups was compared by X2 test. Results: Chromosome spreading permitted adequate analyzing in 348 unfertilized oocytes. In 33.6% chromosomal aneulpoidy was observed with the following frequencies; hypo-hyploidy,22/348 (6.4%), hyper-hyploidy, 42/348 (12.2%) and diploidy, 52/348 (15%). The frequency of aneuoplidy was significantly higher in TFF group 33/80 (41%) than PFF group 83/268 (31%),p<0.01, X2. The most frequent numerical aberration was observed in chromosome group, G of the human karyotyped. Conclusion: Since cytogentic analysis of failed fertilized oocytes and sperm function tests are veryhelpful for direct information on low success rate of fertilization, further studies analyzing on both gametes function in TFF cycles will be needed.