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Why a genetic consultation?
The genetic consultation consists in evaluating the probability for a couple to transmit a genetic disease to their future child. The question most often arises for serious illnesses, such as cystic fibrosis, myopathies , hemophilia, mental retardation, a congenital malformation or even a chromosome abnormality, such as trisomy 21.
We can thus speak of “predictive medicine”, since this medical act is an attempt to predict the future and also concerns a person who does not yet exist (your future child).
Couples at risk
The first couples concerned are those in which one of the two partners himself has a known genetic disease, such as hemophilia, or suffers from a potentially hereditary problem, such as certain deformities or stunted growth. Parents of a first child with this type of condition are also more likely to pass a genetic disease to their baby. You should also ask yourself this question if there is one or more affected persons in your family or that of your companion.
Even if it is preferable to consider it before planning a child, a genetic consultation during pregnancy is essential if you are one of the people at risk. Most of the time, it will allow you to reassure you that your baby is in good health and, if necessary, to examine the different possible attitudes.
When an anomaly is detected
Even if the couple has no particular history, it may happen that an anomaly is detected during an ultrasound, maternal blood sample or amniocentesis. In this case, the genetic consultation makes it possible to analyze the anomalies in question, in order to determine whether they are of family origin and then to consider prenatal and postnatal treatment, or even a possible request for medical termination of pregnancy. . This last question can only be asked for serious and incurable diseases at the time of diagnosis, such as cystic fibrosis, myopathies, mental retardation, a congenital malformation or even a chromosome anomaly, such as trisomy 21.
The family survey
From the start of the consultation with the geneticist, the latter will ask you about your personal history, but also about your family and that of your companion. He thus seeks to determine if there are several cases of the same disease in your families, including those of distant relatives or the deceased. This stage can be rather badly lived, because it sometimes makes exhume family stories of sick or deceased children considered as taboo, but it turns out to be decisive. All these questions will allow the geneticist to establish a genealogical tree representing the distribution of the disease in the family and its mode of transmission.
Genetic tests
After determining which genetic disease you are likely to be carriers of, the geneticist should discuss with you the more or less disabling nature of this disease, the resulting vital prognosis, the current and future therapeutic possibilities, the reliability of the tests. considered, the existence of prenatal diagnosis during pregnancy and its implications in the event of a positive diagnosis.
You may then be asked to sign an informed consent allowing genetic tests to be performed.. These tests, very regulated by law, are carried out from a simple blood sample to study the chromosomes or to extract DNA for a molecular test. Thanks to them, the geneticist will be able to establish with certainty your probabilities of transmitting a specific genetic disease to a future child.
A decision in consultation with the doctors
The role of the geneticist often consists of reassuring couples who have come to consult. Otherwise, the doctor can provide you with objective information about the illness from which your baby is suffering, to fully understand the situation and thus allow you to make the decisions that seem best to you.
All this is often difficult to assimilate and most of the time requires further consultations, as well as the support of a psychologist. Anyway, be aware that, throughout this process, the geneticist will not be able to consider performing the tests without your consent and that all decisions will be taken jointly.
Special case: preimplantation diagnosis
If the genetic consultation reveals that you have a hereditary anomaly, it can sometimes lead the geneticist to offer you a PGD. This method makes it possible to search for this anomaly on embryos obtained by in vitro fertilization. (IVF), that is, before they even develop in the uterus. Embryos that do not carry the anomaly can thus be transferred to the uterus, while affected embryos are destroyed. In France, only three centers are authorized to offer PGD.
See our file “ 10 questions about PGD »