The contribution of CHROMOSOMES abnormalities, genes disorders on reproductive pathology was documented since many years from post and prenatal investigation. Many factors have been pointed to affect the survival rate of embryos from fertilization to the blastocyst stage. Among them are inappropriate maternal age and paternal factors (Janny and Menezo et al., 1994), ovarian stimulation protocols, genic and epigenic oocyte maturation and culture conditions (Moor et al., 1998) combined to growth factors lack (Kaye, 1997) and pre or post zygotic chromosomal and/or nuclear abnormalities (Benkhalifa et al 2004).
An increase of gametes chromatin packaging abnormalities, externalization of phosphatidylserine and DNA fragmentation by apoptosis may cause fertilization failure and oocyte activation (Burello et al 2004). Also a complete absence of spindle formation in association with immature ooplasm can show a complete development oocyte arrest after ICSI (Windt ML et al 2001). It was hypothesized that female infertility due to abnormal oocyte structure and abnormal zona pellucida and causing natural conception failure can be resolved by ICSI ( Paz et al 2004) but ovarian stimulation for ART can affect zonna pellucida thickness and structure as well as oolemma difficulty penetration during ICSI (Ebner T et al 2002).
Anomalies of the centrosome (Navarra et al. 1997), defects in "oocyte activating factor" (Dozortsev et al. 1995) and in DNA condensation (Sakkas et al. 1997) may also affect oocyte activation and early zygote cleavage. In severe male subfertility, the most sperm head defects are disorders of nuclear membrane, acrosomal cap and chromatin structure desorganisation, these defects seem to be associated with dysfunctional sperm-oocyte recognition, binding and fusion with oolemma (Kupker et al 1998). Antisperm antibodies (Naz et al.1992) may block early embryogenesis and poor quality sperm can also induce delays in the S-phase of the first cell cycle.
Gametes manipulation for ART can increases the risk meiosis defect, anaphase lag and chromosome non disjunction. Cytogenetic anomalies are responsible for the arrest of least one half of obtained embryos in ART program (Benkhalifa et al. 1996). These anomalies can obviously arise due to maternal and paternal problems (i.e. chromosome abnormalities in gametes, Aran et al. 1999) or to CHROMOSOMES segregation disorder during early cleavage.
Morphological and cytogenetic analysis of intact oocytes and blocked zygotes after IVF and ICSI demonstrate that 20 % of metaphase II oocytes had an abnormal Karyotype (Benkhalifa et al 2003). Pre-zygotic stage investigation (Verlinsky et al 2003) showed a high rate of CHROMOSOMES aneuploidy on first and second polar bodies. Preimplantation aneuploidy screening of early embryos demonstrate that chromosome disorders and apoptosis (originated from gametes, zygote and or embryos) are common causes of early embryo blocking, repeated implantation failure and recurrent spontaneous abortion in ART practice.