A well-known factor is that 50% of infertility cases are the man's fault. Failures in the male reproductive function have different symptoms: abnormal semen viscosity, changes in the quality of ejaculate (astheno-, oligo-, terato-, azoospermia), antispermal immunity. Such violations occur for different reasons. Adverse effect is exerted by congenital urological diseases, such as varicocele or cryptorchidism, chronic inflammatory diseases of the urogenital tract, complications after herniotomy, infectious parotiditis, trauma, etc.
Failures in reproductive function may be based on genetic factors, for example, mutations in genes that control spermatogenesis, or quantitative and structural chromosomal abnormalities. These violations can be identified with the help of molecular-genetic and cytogenetic diagnostic methods.
According to the existing information, there are much more chromosomal abnormalities in infertile men than in male newborns. (Chandley, 1984; Retief, 1984; Bourrouillou, 1985; De Braekeleer, 1991; Pandiyan, 1996). This statement is valid in relation to the patients suffering from such forms of infertility, as pronounced oligozoospermia and azoospermia. Based on recent studies, men who were included into the ICSI or IVF program, have a higher index of chromosomal abnormalities, in comparison with the population level. (Peschka, 1996; Testart, 1996; Meschede, 1998; Gekas, 2001).
In 1996 Testart carried out karyotyping of 261 infertile couples who were going to perform the ICSI procedure; chromosomal abnormalities were identified in 4.2% of cases in men and in 1.1% of cases in women. In the same year, Bonduelle tried to reveal the presence of similar anomalies among parents of 877 children who were born as a result of ICSI. Abnormalities were found in nine men and only two women. A year later, Mau examined 150 married couples who had gone through the ICSI procedure. Amount of chromosomal abnormalities in men was 12%, in women - twice less.
In 2001 Gekas et. al. investigated the results of karyotyping of married couples who had gone through the ICSI procedure. As a result, there were found 183 abnormalities, moreover this figure in men was 6.1%, and in women - 4.84%.
Chromosomal abnormalities are referred to as causes affecting the outcome of IVF (Simpson, 1992), as well as the quality of implantation (Scholtes, 1998). Despite this evidence, there is no reason to claim that there is a direct dependence between infertility and chromosomal abnormalities. These anomalies are poorly studied; the largest research published in 1977, was based on cytogenetic analysis of a small amount of cells. In addition, the identification of such anomalies, in some cases, is taken as a norm, when it comes to the patients who have no symptoms of the disease. It also hasn't been determined, what minimum percentage of aberrant cells is required in order to allow classification of karyotype as an actual mosaicism, rather than a low level mosaicism (Mitelman, 1995).
One study reports that low-level mosaicism of sex chromosomes, taken for analysis from married couples who were recommended ICSI, and from a control group of men and women, whose pregnancy has been registered within 2 years, is comparable. (Peschka et.al, 1999).
Over the last thirty years (Chandley et. al., 1975; Chandley, 1979) it is already not a secret for anyone that there is a direct connection between male infertility and existing abnormalities in men karyotype. Furthermore, it is known that the possibility of chromosomal abnormalities presence is inversely proportional to the number of sperm cells in semen (Nagvenkar et. al., 2005). Because of this, any deviations in spermogram of a man suffering from infertility are an indication for karyotyping.
There is also an established connection between the morphological structure of sperm cells, their mobility and the number of chromosomal abnormalities (Bourrouillou, 1992). But such connection has not been confirmed in more recent studies (Testart, 1996), which makes it possible to admit such a fact that problems with fertilization are a symptom of chromosomal abnormalities. Data is extremely controversial, so the observations, which differ in their results, should be excluded as soon as the necessary amount of data is accumulated.
The group of "polymorphisms" is of a special scientific interest. Such factors as changes in the structure of chromosomes, reduction of their size, or, conversely, an enlargement that occurs due to the changes in satellite DNA strands or areas of heterochromatin in the sex chromosomes or autosomes, are polymorphic variants of karyotype. This can contribute to failure in the process of chromosome segregation, resulting in unbalanced abnormalities in fetal karyotype.
The biological significance and nature of polymorphism need to be investigated, and this task is currently one of the most problematic. During these years there has been already collected quite a lot of the actual material. It involves data on people with normal health and on patients suffering from various chromosomal abnormalities. There is information that similar chromosomal pathologies in the normal population occur in 4-6% of cases (Hsu et al, 1987, Demidov et al, 1990).
As some authors have found, among patients suffering from congenital abnormalities, carriers of the 1st and 9th chromosomes are more frequent. And there is still no consensus about the role of centromere heterochromatin variants in the development of any pathology.