The influence of chromosomal abnormalities on oocytes failing to fertilize after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and the relationship between survival of the human preimplantation embryos generated in vitro and chromosomal abnormality was investigated.
In this study, 364 human unfertilized oocytes after IVF or ICSI were cytogenetically analysed using trakowski's air-drying and 238 embryos of varing morphology between the eprenuclouse and eight cell stage by Dyban's air drying method.
In the oocytes with countable metaphase chromosomes, haploidy rates was 39% and aneuploidy rates was 61%. Chromosomes abnormalities of the other types such as structural abnormalities (5.2%), polypoidy (2.8%), sperm PCC (14.3%), chromosomes stickiness (5.8%) and decondensation of oocyte chromatin (6.6%) was also observed.
High frequency of chromosomal abnormalities among embryos analysed in this study was observed. The overall abnormalities found for embryos was 89.8%. cleavage stage embryos with poor morphology showed a higher incidence of chromosomal abnormalities (95.4%, 103 out of 108 analysed embryos) than those with good morphology (68.9%, 20 out of 29 analysed embryos). In both IVF and ICSI generated embryos. Aneuploidy was the most frequently observed abnormality (46.7%). In addition various types of aberrations such as triploidy (2.2%), hoploidy (1.5%), mosaicism (33.6%) or structural abnormalities (5.8%) was also observed.
Although the total chromosomal abnormalities in ICSI generated embryos was found to be higher (8.8.6%), then embryos generated in IVF, but there is no statistical significant difference between these two groups.
In conclusion, the main points emerged from our results are as follows:
1. Aneuploidies are the major cause of fertilization failures in oocytes and implantation failure of embryos.
2. There is no significant difference between the frequency of chromosomal abnormalities in unfertilized oocytes and embryos generated in IVF and ICSI procedures.
3. The maternal age may have an influence on oocytes aneupliody rates and cause aneuploid embryos leading to in vitro fertilization failure.
4. There is an association between chromosomal abnormality and embryo morphology.
5. Chromosomal abnormality may have a direct influence on pregnancy rate.
Our results therefore, emphasize the need for a reliable non-invasive method for recognition and detection of chromosomally normal embryo for transfer. The development of such methods could appreciable increase the success rate in the IVF procedures.