Genetics is a field of science that has always fascinated us; just take look at how many front pages and news stories cover such advances – remember Dolly the sheep, or the Human Genome Project? We continue to be fascinated, engaged and excited by such advances, recognising that only by pushing the boundaries of medical research will we understand the true nature of hereditary disease; improve its prevention and develop effective treatment and therapies.
Advances in the field of genetics and new technologies have rapidly increased momentum in the field of reproductive medicine. The development of techniques such as Preimplantation Genetic Diagnosis, Test qCarrier (Preconceptional Genetic Test) and non-invasive Prenatal Tests have been used effectively in cases where the health of a baby might be compromised.
The Medical Genetics Unit at Dexeus Mujer has been at the forefront of the use of these techniques in the gynaecological field. Since its inception, the Unit has worked closely with the reproductive medical team in order to evaluate each patient and be in the best possible position to offer appropriate advice and treatment where required.
The science of Genetics is complicated and not surprisingly, for many, it is a science which is difficult to grasp
What are chromosomes and genes?
The science of Genetics is complicated and not surprisingly, for many, it is a science which is difficult to grasp. At Dexeus Mujer, our geneticists take time to explain, interpret and share genetic information in the most accessible manner possible. We want to ensure all our patients fully understand their specific medical position and are aware of all the genetic risks associated with it.
So, let’s start by understanding the basic elements: chromosomes and genes. Chromosomes are structures that contain all the genetic information of a human being. In every cell of our body, there are 46 chromosomes, or 23 pairs. Each pair is composed of a chromosome that has been transmitted by the mother and one from the father. The first 22 pairs are common in men and women, but chromosome 23 defines the gender of the individual: it is composed of two chromosomes, X and Y; XX for females and XY for males.
The genetic information contained in the chromosomes are stored as genes, which are found in the nucleus of every cell. There are more than 20,000 genes in each cell and each one of them has one or more specific functions in our body. Each person inherits 23 chromosomes from each parent at the time of fertilization. If however there is a dysfunction caused by a defect in some of the genes, mutations that cause genetic diseases appear.
When should you ask for genetic counselling?
The Medical Genetics Unit at Dexeus Mujer offers personalized advice to anyone who wants to evaluate potential risks and learn about diagnostic tests, prevention and detection of genetic abnormalities.
The study the clinical history of patients, as well as family history to assess potential risks and inform you of all the available options which are currently provided in the field of reproductive medicine.
Genetic counselling service is offered to any person who requests it, although there are certain circumstances in which the visit is particularly recommended:
- If either member of the couple has a personal or family history of hereditary diseases or cancer
- If the couple are closely related
- Unfavourable reproductive history (repeated miscarriages, or a history of foetal genetic abnormalities in previous pregnancies)
- If there is suspicion of a fertility problem of genetic origin
- If there is the existence of some genetic alteration or pre-tests indicate a possible foetal genetic problem
The first pregnancy after a PGD in Spain was carried out at our centre in 1994
Which techniques are applied?
Preimplantation Genetic Diagnosis
Preimplantation Genetic Diagnosis (PGD) allows for the study of the genetic characteristics of embryos before transferring them into the uterus to prevent the future baby being born with diseases that are genetically transmitted.
After an IVF cycle, we obtain embryos from which we extract a cell that will be analysed to check if there is any anomaly, in order to select those that are most viable. Thanks to this analysis, the likelihood of abortion decreases considerably.
The implementation of the PGD technique is useful when there is a chromosomal rearrangement (translocations and inversions of the chromosomes) in a member of the couple, thus minimizing the difficulties conceiving or possible birth defects.
In certain cases, the number of chromosomes that are received from parents is lower or higher than the 23 that should transmit both father and mother. This error in the transmission of chromosomes is called aneuploidy and it can cause physical or intellectual disorders in the baby (such as Down syndrome or trisomy 21).
Preimplantation genetic diagnosis is used in cases of advanced maternal age (>37 years), in altered male meiosis and in couples with repeated miscarriages or repeated implantation failures.
The first pregnancy after a PGD in Spain was carried out at our centre in 1994 in collaboration with the Universitat Autònoma de Barcelona (UAB) to prevent the conception of a child with haemophilia in a couple whose mother was a carrier of the disease. From this moment on there have been many couples who have benefited from this technique.
The Preconceptional Genetic Test (qCarrier)
Dexeus Mujer was one of the first clinics to incorporate the genetic testing of carriers in all its reproduction treatments. Through this test, we identify in future parents the presence of genes that cause genetic diseases such as cystic fibrosis, spinal muscular atrophy, the thalassemia, congenital hypothyroidism or Fragile-X syndrome. All of these are diseases that parents can transmit to their babies which can cause serious health problems in the child. These genetic tests are valid for any person regardless of their race or country of origin – all hereditary diseases are not specific to any ethnicity.
What does the test consist of? We only need to obtain a blood sample from the parents to analyse their DNA. If they are carriers of some genetic alteration, we can assess the probability of the couple passing on a genetic disease to a baby and this test will allow us to adjust treatment if necessary.
In the case of In Vitro Fertilization with donated eggs, our protocol is to perform the carriers test to all egg donors, so it is essential that the recipient’s partner also performs the test to verify whether both are carriers of the same mutation.
The carrier of a genetic disease is someone who doesn’t suffer from the disease, but it can pass it on to his/her children. Carriers do not tend to have health problems arising from the genetic disease and may not have any family history of it.
The probability that the carrier of a genetic disease has a child affected by it depends on the form of transmission of the disease. The genetic testing of carriers is performed to recessive genetic diseases, in which a baby would be affected only if the two copies that it receives from both parents carry the alteration associated with that partiocular disease.
10 of every 1,000 children are born with diseases of a genetic type.
There is a 25% probability that children will suffer from the disease if both parents are carriers.
The carrier of a genetic disease is someone who doesn’t suffer from the disease, but it can pass it on to his/her children
For patients who are already pregnant and wish to rule out any risk of chromosomal abnormalities in the future baby, we offer the non-invasive Prenatal Test and the Molecular Prenatal Diagnosis (Array CGH).
The non-invasive Prenatal Test is a test that can be performed starting in week 10 of pregnancy, and through an analysis of the mother’s blood we detect the most frequent chromosomal abnormalities: Down syndrome, Edwards syndrome and Patau syndrome. In addition to these diseases the test. In some cases, allows you to detect other genetic disorders known as microdeletions, which are small losses of genetic material that are associated with serious problems of development in the new-born.
In addition, Dexeus Mujer offers the Molecular Prenatal Diagnosis, also called Array CGH (Comparative Genomic Hybridization) or Prenatal Molecular Karyotype. This is a last generation technique for genetic diagnosis that allows us to diagnose chromosomal abnormalities with a higher resolution than conventional techniques. It provides a quick and precise tool for the study of the human genome that detects alterations in DNA, including microdeletions and duplications, and it is obtained through a sample of the placenta or amniotic fluid through a chorion villi sampling or amniocentesis.
Cancer Risk Test (qCanceRisk)
Our Unit of Genomic Medicine also collaborates with the specialized women’s cancer unit based in Dexeus Mujer. With the Cancer Risk Test or qCanceRisk we can identify the hereditary genetic predisposition to breast cancer by analysing more than 200 genes. This test is carried out using a blood sample (or saliva if it is not possible to perform the extraction), from which we get DNA to detect the presence of mutations.
For a healthy baby
Thanks to the knowledge of the human genome, we have been able to boost the development of personalized medicine in our centre, with diagnostic techniques that allow us to prevent genetic abnormalities in order for our patients be parents of a healthy baby.
We have over 80 years experience in caring for women’s health and Dexeus Mujer is committed to help all those people whose babies’ health might be compromised by a genetic disorder. The rapid development of technology is allowing us to increasingly avoid serious diseases to the offspring and to ensure that couples can enjoy such a long awaited pregnancy.
More information can be found on the Dexeus Mujer website en.dexeus.com