Infertility is an illness that affects the reproductive system and is characteristic of the inability to attain a clinical pregnancy after 48 weeks or more of usual unprotected sex. In all cases of infertility, 40-50% are represented by female infertility, whereas male infertility accounts for 30-40% and the rest of 30% is not known or is accounted for by both male and female infertility (Dyer et al., 2016). The Federal Statistical Office indicates that the cause of unintentional childlessness in infertile couples looking for aided reproductive technology can be ascribed to 11% male infertility to 24% female infertility, and 40% to both couples. Nevertheless, the cause for infertility in 25% cases is unexplainable. Studies have indicated that there is a high probability of the existence of genetic abnormalities such as gene mutations and chromosomal anomalies in infertile couples. Advances in genetic studies have led to the introduction of vitro fertilizing methods, and as a result, there exist genetic tests to ascertain the reasons for infertility and examine the risks of a partner to transmit its genetic features. This enables partners who are at-risk to make a well-versed decision when opting for a clinically aided reproduction. Additionally, it allows the practitioners to carry out a prenatal assessment if need be. The objective of this review is to present detailed information on genetic testing of infertile couples. The study is divided into three parts: Overall Reflexions on Genetic Testing, Genetic Testing in Male Infertility, and Genetic Testing in Female Infertility.
This unprotected sexual contact. The period of 12 months is provided for by the WHO (n.d.). Infertility exists when pregnancy can only be attained via aided reproduction or if the partner is wholly impotent.
Genetic testing is usually carried out using three methods based on the current difficulty: molecular cytogenetics, chromosome analysis, or molecular analysis of DNA. The chromosomal analysis gives a summary of all chromosomes, which is adequate for ascertaining aneuploidy. Fiorentino et al. (2014) define aneuploidy as the arithmetical change from the normal number of 46 chromosomes like the case of Turner syndrome. Aneuploidy also enables the recognition of changes in structures such as translocations responsible for abortions. Fiorentino et al. (2014) further observe that the discovery of the changes in the structures is significantly dependent on the microscopic resolution. The German Society of Human Genetics recommends a minimum of 550 bands per haploid set of chromosomal banding resolution in a situation where partners have experienced repeated abortions. Greater microscopic resolutions within the microscopic range allow molecular cytogenetic testing. Contrariwise, this approach is rarely used in fertility tests. Furthermore, gene mutations require high-resolution tests for instance deletions in the azoospermia factor area or FMR 1 gene mutations (Fiorentino et al., 2014).
Multiple scientific research has reliably indicated the prevalence of chromosomal aberrations is the cause of infertile in couples irrespective of the cause of infertility. It is therefore also recommended by multiple genetic testing guidelines and research that genetic testing should commence with chromosome assessment at all times (Zorrilla and Yatsenko, 2013). A minimum blood sample of 2ml diluted with heparin is recommended. However, a minimum of 5 ml blood sample augmented with EDTA is needed in the case of molecular genetic analysis (Fiorentino et al., 2014).
The leading cause of infertility in males are chromosomal aberrations, gene mutations (cystic fibrosis trans-membrane receptor gene (CFTR)), and micro-deletions of Y chromosomes (Hotaling and Carrell, 2014). Research on families of infertile couples shows that there is a likelihood of a familial aspect in male infertility leading to a suggestion of an inherited autosomal-recessive mechanism (Soubry et al., 2014). Hotaling and Carrell (2014) observe that in male infertility, azoospermia and advanced oligozoospermia are the primary pointers for genetic testing after semen assessment. Genetic testing should be carried out even if the discovery of genetic alteration is less likely to alter the diagnosis. This is to ensure that a causal diagnosis is finalized and the hereditary threat factor for the progenies is assessed in case of favorable intervention (Hotaling and Carrell, 2014).
Karyotype analysis is used to detect numerical and structural chromosomal abnormalities. Chromosomal anomalies in infertile men are estimated to be approximately ten times higher than the overall population, with a variation of 2% to 16% and declining sperm count and increasing rate of aberrations of autosomes (Zhang et al., 2015). The infertile individual is in most instances healthy except for syndromic cases. Contrariwise, translocation cases such as a distinctly high risk of inducing pregnancy which will end up being a stillbirth or miscarriage or an offspring with different levels of psychological or/and physical disability due to an uneven set of chromosomes in the child (Hotaling and Carrell, 2014). Thus, karyotype assessment is necessary for males diagnosed with azoospermia or oligospermia, which should be followed by genetic psychotherapy.
The number of males with Klinefelter syndrome are markedly higher among infertile men and have the following clinical symptoms azoospermia (fewer sperms in the ejaculate), reduced volume of the testis, high levels of gonadotropin, reduced concentrations of the serum testosterone, and body structure that appears feminine. Azoospermia is the prevalent cause of infertility in Klinefelter patients. The discovery of vitro fertilization alongside intracytoplasmic sperm injection (ICSI) has increased the opportunity for Klinefelter men to have their children. The latest research has shown that spermatozoa outcomes for ICSI are 30-70% successful when the testicular sperm extraction (TESE) is utilized (Madureira et al., 2014). However, during the initial identification of Klinefelter syndrome, it is essential that the practitioner to discuss with the client for the possibility of TESE even if conception is not presently needed (Hotaling and Carrell, 2014).
Y-chromosomal microdeletions
Couples diagnosed with advanced oligozoospermia or mild azoospermia is supposed be examined for the existence of microdeletions of the Y chromosomes, which are some of the least detected genetic causes of spermatogenetic aberrations causing infertility in males (Giacco et al., 2014). Hamada et al. (2013) identified five primary microdeletion forms namely AZFa, AZFc, AZFb, P5-distal P1 AZFbc, and P4-distal P1 AZFc as shown in Figure 2.1. It is ascertained that microdeletions of the Y chromosome take place in men that are infertile except for control men, however at a varying rate between states, based on the criteria of selection of the participants and their ethnicity (Giacco et al., 2014). Overall, men with azoospermia experience increased rates of microdeletions than those diagnosed with oligozoospermia (Hotaling and Carrell, 2014). This is indicated by the semen features which point out that 50% of the patients have azoospermia and few spermatozoa present in the remaining 50% ejaculate (Hotaling and Carrell, 2014). Recurrent semen assessment is vital for such patients because of the possibility of re-occurrence of the spermatozoa in the ejaculate and is utilized for ICSI.
Men with AZFc deletions can re-gain sperms by 50% using TESE. However, none has been retrieved in cases of AZFb and AZFa deletions. Thus, molecular genetic testing is left as the most appropriate for such patients with prognostic value for TESE. Inactivation of the mutations may lead to primary or secondary amenorrhea, POF, and infertility, whereas activation of mutations is likely to expose to ovarian hyperstimulation syndrome (OHSS) caused by the administration of exogenous FSH or even with instant inception (Desai et al., 2013).
Female infertility is primarily caused by repeated pregnancy loss (RPL), premature ovarian failure (POF), and polycystic ovary syndrome (PCOS).
High PCOS vulnerability is linked to multiple genes that regulate the function and metabolism of the ovary. However, none is sufficiently powerful to individually correlate with the vulnerability of the illness or response to therapy. Several research have examined polymorphisms in the gene encrypting FSH receptor. In the study by Dewailly et al. (2013) a single nucleotide polymorphism (SNP) in the tenth exon of the FSHR gene was unfailingly detected being with a substantial relationship with ovarian feedback to FSH. However, it did not appear to have any vital function in the PCOS. According to Yan et al. (2013), the FSH quantity required for regulated ovarian hyperstimulation to attain the same level of estradiol was markedly lower in females having the N/N genotype at point 680, pointing out to decreased sensitivity of the ovary to FSH in vivo for an allele of the similar position.
Repeated pregnancy loss is justified when it repeatedly takes place thrice or more in unprompted abortions before 20weeks of gestation. RPL takes place in 1% of all pregnancies. Studies have suggested that specific immunological and thrombophilic abnormalities are the possible causes of RPL (Keltz et al., 2013). Additionally, the authors have estimated that a quarter to half of the miscarriages in patients with RPL are related to conceptus chromosomal abnormality, and karyotyping of abortuses need to be undertaken to ascertain a cytogenetic basis for the loss (Larsen et al., 2013). Pasquier et al. (2015) conducted abnormal tests on women with over two RPL and indicated that there is a need for an entire assessment of the evidence-based factors such as uterine anatomy, parental karyotyping among others. Furthermore, the author suggests the recommendation of TSH to all partners with over two successive losses of pregnancy. However, there is a need for restraint during the analysis of the outcomes of an abnormal assessment because the factor ascertained may not be the cause for the loss of pregnancy.
Premature ovarian failure
POF is described as a deficiency of the primary ovary characterized by principal amenorrhea or early exhaustion of the ovarian follicles before forty years (Chapman et al., 2015). There is extreme heterogeneity about the causes of POF. It is necessary to carry out Karyotype assessments in primary amenorrhea and when the disease is diagnosed at a tender age. Studies have found that gene mutations influence the functions of hormone and follicle in humans, but they are not mutual (Sherman et al., 2014). Oogenesis process involves genes i.e. RNA linking proteins, transcription features, and DNA linking proteins. Credible mutations that cause POF have been found in few women, however, in erratic instances. Therefore, significant heterogeneity is present in POF, and no specific genetic testing approach can be most appropriate except for karyotype. Sherman et al. (2014) elucidate that pre-mutations or mutations of gene FMR1 are considerably linked with secondary amenorrhea in women kinsfolks of males diagnosed with psychological problems.
A chance to foretell the possibility of premature menopause can be determined to sue early diagnosis of POF in the family, an aspect that will also enable the assessment of varying choices of reproduction such as giving birth earlier or freezing embryos. Jankowska (2017) suggests that practitioners should carry out diagnosis on time and initiate managing the symptoms, risk minimization, and emotional support, due to the severe aggregate negative impacts of POF (Sherman et al., 2014). It is recommended that genetic counseling is undertaken for multiple reasons, once any genetic type of POF is detected. According to Sherman et al. (2014) counseling is beneficial in instances where families are associated with mental retardation.
Conclusion
Most couples affected by infertility and the associated illnesses have resorted to aided reproductive technology (ART). Studies have indicated that increasing age in women nears to menopause. Additionally, the practice of delaying childbirth favors the use of ART. However, the efficacy of CSI treatment has led to concerns such as pregnancy complications and congenital disabilities. This necessitates the need for genetic testing which enables early detection of risks and mitigations through expert guidance and counseling.
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