Introduction: Presence of 2 pronuclei (PN) and 2 polar bodies (CP) is usually related with normal fertilization and a diploid state, while those with a different PN number are routinely discarded being considered as abnormal. The aim of this study was to contribute with new data to the knowledge of chromosomal status and developmental potential of apronuclear and unipronuclear zygotes. Materials and Methods: Three hundred andforty six ICSI embryos from the PGD program were classified in 3 groups: (1) 2PN 2CP (n = 264); (2) 0PN 2CP (n = 65) and (3) 1 PN 2CP (n = 17). Presence of pronuclear formation was evaluated 16-20 h after oocyte insemination. Cytogenetic analysis of day 3 biopsied embryos was performedfor chromosomes 13, 15, 16, 18, 21, 22, X and Y in aneuploidy screening cases andfor the chromosomes involved in the reorganization for translocation carriers. Results: Percentages of chromosomally normal embryos were: 26.2% (group 1), 40% (group 2) and 14.3% (group 3). Embryos derivedfrom apronuclear zygotes showed significantly higher developmental competence (p<0.05), with a higher blastocyst formation rate (56.6% vs 16.5%, and 56.6% vs 7.2%). Conclusions: Embryos derived from unipronuclear zygotes should be discarded not only due to their chromosome constitution but also to their low developmental competence. Embryos from apronuclear zygotes (group 2) could be consideredfor transfer. The higher rates of normal chromosomal content and developmental potential found in the group 2 suggest that this pool of embryos could be in fact, early cleavage embryos, and therefore associated with better implantation and pregnancy rates.
|Journal||Revista Iberoamericana de Fertilidad y Reproduccion Humana|
|Publication status||Published - 1 Jan 2007|
- Early cleavage