PRE-CONCEPTION GENETIC SCREENING
PRE-CONCEPTION GENETIC SCREENING, FOR REDUCING THE RISK OF A GENETIC DISEASE IN FUTURE NEWBORNS
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Dear Patients, before planning a family we would like to bring your attention to the possibility of carrying out several genetic tests that could help considerably reduce the risk of a serious genetic disease in your future children. Today, 8,000 monogenetic diseases are known, meaning they depend on genetic alterations to one single gene. Among these, approximately 1,200 are recessive, which means they can be transmitted from the parents (healthy carriers) to their children. Genetic diseases are rare if considered individually, but together they affect one child in every 200 and are responsible for 20% of child mortality. There are no treatments today for curing genetic diseases.
The only possible strategy is prevention: ProCrea offers the most advanced genetic testing to inform the couple about the risk and put it in the right conditions to make the best choice.
In addition to the personal history, there are several indicators to help assessing the presence of genetic diseases:
- In people with infertility problems the prevalence of certain genetic diseases is higher than in the normal population
- there are situations with a higher risk (please tell your doctor), which include:
● consanguineous partners (for example, cousins)
● Ashkenazi Jewish origins
● Arab origins
Genetic tests involve a normal blood withdrawal. The waiting times for results vary between 10 and 15 working days depending on the type of test.
Considering the most widespread genetic diseases in the western population, there are five most important screenings:
ANALYSIS OF THE KARYOTYPE
This is the numerical and structural study of all the cell chromosomes. One cause of infertility in women and men can be an abnormality at the level of the karyotype, whether of the numeric (sexual chromosomes) or structural type (balanced translocations or other anomalies that do not involve loss or gain of genetic material). It is recommended to examine the karyotype in cases of infertility to determine whether there is a risk for the couple of giving birth to a child with malformations and severe psychomotor retardation.
GENETIC TEST FOR CYSTIC FIBROSIS (CFTR)
One of the most common recessive genetic diseases is cystic fibrosis (or mucoviscidosis): one in 25 people report a mutation in the CFTR gene (more than one thousand different mutations are known in this gene); the disease manifests in 1 individual out of 2,500. Infertility in humans can be a symptom of the presence of a mutation in the gene responsible for this disease. The test examines the 50 most common mutations in Central Europe that account for more than 90% of the cases reported. If a partner turns out to be the carrier of a mutation, on demand ProCrea can perform a second-level test on the partner in order to more accurately assess the risk of conceiving a child with this disease.
TEST FOR SPINAL MUSCULAR ATROPHY (SMA)
SMA is a neurodegenerative disease that affects nerve cells called motoneurons which control the voluntary muscle movements (lower limbs and respiratory muscles). This disease - the first cause of death for childhood genetic disease - affects 1/6,000 - 1/10,000 live births; with a frequency for carriers of 1/40 to 1/60. It is a recessive autosomal disorder, therefore it only manifests if both parents (without symptoms) carry a mutation of the SMN1 gene. A negative result for this test in one of the partners diminishes the risk of having a baby with SMA by 1/90,000.
FRAGILE X SYNDROME: DETERMINING PREMUTATION
The Fragile X Syndrome is the most frequent cause of hereditary mental retardation (approximately 1/4,000 males affected). This syndrome is caused by the abnormal expansion of a piece of gene, the FMR1, consisting of a sequence repeated various time and located on the X chromosome. Being related to the X chromosome, males are usually more affected by females. The disease will only be 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" areas. It is only the latter, when unstable - that is, when it stretches with the passing of the generations - which causes syndrome in later generations. The instability is only found in the passage from the mother to the child and not from the father to the child. Caucasian people are estimated to have a premutation of approximately 1/150-250. The test to determine if a premutation is present is very important for establishing whether there is any risk of conceiving a child with the syndrome and in this case, of being able to propose a prenatal or pre-implantation analysis. The result is also important for determining whether there are other women in the family at risk of transmitting disease.
BIOCHEMICAL SCREENING FOR THE HAEMOGLOBINOPATHIES (THALASSEMIAS)
The thalassemias form part of the group of hereditary diseases called haemoglobinopathies and are characterised by chronic anaemia of varying severity due to a quantitative defect in the haemoglobin production. In the Mediterranean region, two forms of haemoglobinopathy are common: beta-thalassemia and sickle-cell anaemia (or drepanocytosis), both highly disabling, with a frequency of carriers ranging between 1 and 15%. Also in this case, it is a recessive disease in which both partners in the couple are carriers and can transmit the disease to their children. It is possible to discover possible carriers thanks to a series of biochemical tests (total blood count, HbA2 dosage, HbF dosage, ferritinaemia, etc.). Only in case of doubt will it be necessary to proceed with the genetic test to detect mutations in the genes that encode the haemoglobin.