Other preconception analyses

This is the numerical and structural study of all the chromosomes in the cell. A cause of infertility in women and men can be determined by an abnormality at the level of the karyotype, either numerical (sex chromosomes) or structural (balanced translocations or other abnormalities that do not involve loss or gain of genetic material). A karyotype examination is recommended in cases of infertility to determine whether the couple is at risk of giving birth to a child with malformations and severe psychomotor retardation.

Among the most common recessive genetic diseases is cystic fibrosis (or mucoviscidosis): one in 25 people on average carries a mutation on the CFTR gene (more than a thousand different mutations on this gene are known of); the disease occurs in 1 in 2,500 individuals. Male infertility may be a symptom of the presence of a mutation on the gene responsible for the disease. The test examines the 50 most common mutations in Central Europe, covering more than 90% of reported cases. If a partner is found to be carrying a mutation, Next Fertility ProCrea will, on request, perform a second level test on the partner in order to more accurately assess the risk of conceiving a sick child.

SMA is a neurodegenerative disease in which nerve cells called motor neurons that control movement of voluntary muscles (lower limbs and breathing muscles) are affected. This disease – the leading cause of death from childhood genetic disease – affects 1/6,000 – 1/10,000 live births; with a carrier frequency of 1/40 – 1/60. It is an autosomal recessive disease, so it only occurs if both parents (without symptoms) carry a mutation in the SMN1 gene. A negative result of this test in either partner decreases the risk of having a child with SMA to 1/90,000.

Fragile X syndrome is the most common cause of inherited mental retardation (about 1/4,000 affected males). The syndrome is caused by the abnormal expansion of a small piece of gene, FMR1, consisting of a sequence repeated several times and located on the X chromosome. Because it is linked to the X chromosome, males are usually more affected than females. The disease is only present if the expansion exceeds a certain number of repetitions (complete mutation). Between the normal number of repetitions and the complete mutation are the “intermediate” and “premutated” zones. It is only the latter, when unstable – i.e. lengthening with the passing of generations – that causes the syndrome in subsequent generations. Instability is practically only found in the transition from mother to son/daughter and not from father to son/daughter. In the Caucasian population, premutation carriers are estimated to be around 1/150-250. The test to determine if premutation is present is very important in order to establish if there is a risk of conceiving a child with the syndrome, and in such case propose a prenatal or preimplantation analysis. The result is also very important in determining whether there are other women at risk of transmitting the disease within the family.