ABSTRACT
Background: Present knowledge of mechanisms involved in human fertilization has uncovered a new group of pathologic conditions that have been generically named fertilization abnormalities. Aim: To determine the contribution of chromosomal alterations to in vitro fertilization failures. Material and methods: A cytogenetic analysis of oocytes that were not fertilized after insemination with normal spermatozoa. Oocytes were obtained from patients subjected to in vitro fertilization in a public hospital of Metropolitan Santiago. Ovulation was induced in these patients administering GnRh-a, FSH, HMG and HCG. The double fixation technique described by Wramsby was used to obtain chromosomes. Results: One hundred and seven oocytes coming from 45 women aged 25 to 42 years old were studied. The frequency of aneuploidy in these oocytes was 37.3 percent, with a 11.8 percent of hypohaploidy, a 21.6 percent of hyperhaploidy and a 3.9 percent of diploid oocytes. In hyperhaploid as well as in hypohaploid oocytes, the chromosomes involved in aneuploidy pertained to groups D and G. Conclusions: Although the total frequency of aneuploidy is within normal ranges, the frequency of hyperhaploidy is superior to previous reports. An explanation for this finding could be that the occurrence of a lack of disjunction with chromosomal retention in the parental cell occurs with a higher frequency than that in which the chromosomes are retained in the polocyte. We also suggest that oocyte chromosomal aneuploidy could contribute to the failure of in vitro fertilization procedures (