Do you want a healthy baby? Spend money on a preconceptional test!

The test will reveal the risk of having a seriously ill child

Vladimir Fradkin, Deutsche WelleUntil now, expectant parents have not had the opportunity to assess the risk of having a child with severe hereditary diseases.

Now such a test is at their disposal.

In the USA and in Spain, it has already been used in clinical practice since the beginning of this year, in Germany, it seems, it will receive admission in the very near future. We are talking about a preconceptional genetic test of the American company Recombine, headquartered in New York. "Preconceptional" means that the test is intended for future parents and should be conducted before the conception of the child. Its purpose is to minimize the risk of the birth of children with severe hereditary diseases – first of all, the so-called monogenic, that is, those caused by a mutation of a single gene. Such diseases are inherited in accordance with the laws of classical Mendelian genetics.

The total number of monogenic diseases is in the thousands, most of them are rare, many have not even been described yet, but there are also well-known ones like cystic fibrosis, spinal muscular atrophy or Tay-Sachs syndrome. In the genome of almost any person, there are copies of genes with dangerous mutations, but in most cases these mutant alleles are recessive: they do not manifest themselves, so the person remains healthy. The situation is worse if the same gene mutation occurs in both parents: this happens, of course, infrequently, but in this situation the probability of having a child with the corresponding monogenic disease is no less than 25 percent.

Preconceptional test – an alternative to amniocentesisToday, the so–called prenatal (that is, prenatal) diagnostics, specifically amniocentesis, is used to identify possible genetic abnormalities of the embryo.

This is a procedure in which a doctor uses a special needle through the anterior abdominal wall of a pregnant woman to puncture the embryo shell in order to obtain a sample of amniotic fluid for their subsequent laboratory examination: after all, amniotic fluid contains both embryo cells, and their analysis allows you to identify genetic and chromosomal defects. The problem is that, firstly, amniocentesis is an invasive procedure, a puncture of the embryo shell itself is fraught with complications, and secondly, prenatal diagnostics can reveal genetic abnormalities of the fetus only at that stage of its development when the only way out is an artificial termination of pregnancy.

That is why a very interesting alternative is a pre-conception test for future parents, says Professor Jose Horcajadas, scientific director of the European branch of Recombine located in Barcelona: "Couples who decide to have children will be able to find out their, so to speak, initial genetic situation thanks to such a test. And if it turns out that both parents are carriers of the same mutation, then this knowledge will allow them to take appropriate steps to give birth to a healthy child."

Future parents have a choiceUntil now, future parents had the opportunity to be tested only for some very specific diseases that had previously occurred in the family history.

The new test scans DNA for the presence of 180 mutations fraught with hereditary monogenic diseases, including the most common. "In 99 percent of couples, the test result does not give any reason for alarm," explains Professor Orcahadas. – That is, each of the future parents, although there are mutations that can cause monogenic diseases, but not the same ones. However, in one percent of cases, these mutations coincide, and this means a high risk of giving birth to a seriously ill child."

These couples are recommended to resort to in vitro fertilization, that is, to conception in vitro, which will allow preimplantation diagnosis of embryos and choose a healthy one for transplantation into the uterus. But there is, of course, an alternative: to conceive naturally and hope that everything will work out. "Of course, I would not recommend this to anyone," says the Spanish scientist. – It's roulette! But in some countries it is customary to do just that. Although parents know that they have the same dangerous mutation, they take risks, and then, if the fetus has a genetic defect, they have an abortion. Isn't it better to initially take care that the embryo is healthy? However, many couples simply cannot afford artificial insemination. In addition, in a number of countries, preimplantation diagnosis is either prohibited altogether or regulated by excessively strict restrictive laws. I cannot influence these factors."

The test also has influential opponentsThe Recombine company is certainly not the only one in this sector of medical services.

Other firms are developing similar tests today. And this causes concern among some experts. One of them is Stephen Kingsmore, a prominent American physician, director of the Center for Genomic Pediatrics at Mercy Children's Hospital in Kansas City, Missouri. Three years ago, he himself developed a preconceptional supertest capable of detecting a genetic predisposition in potential parents to a thousand hereditary diseases at once. But... "From an ethical point of view, it was very difficult to decide under what circumstances parents should do this test," says Stephen Kingsmore. "We would be faced with the rejection of such a test by the American society – if only out of fear that it would lead to an increase in the number of abortions."

Today, a pediatrician uses his test to scan the DNA of seriously ill children in order to clarify the diagnosis of monogenic diseases. "When dealing with a sick child, we see certain symptoms and know where and what mutations to look for," explains Stephen Kingsmore. – And in the case of a preconceptional test, we don't know this and just scan all the hereditary material – maybe something will be found. But at the same time, purely technical errors are also possible – some mutations will go unnoticed or will be incorrectly identified. The technique is still too imperfect, haste is unacceptable here, it can throw back all medical genetics."

A healthy child is a great successProfessor Orcahadas is not convinced by this logic.

The reliability of the test has been proven in large-scale clinical trials, he says. And as for ethical considerations... "It's really very hard to see parents who have lost a child due to a hereditary disease. They are ready to do anything to prevent this tragedy from happening again. And since we have the opportunity to prevent at least some of the most common monogenic diseases in a child, it's a sin not to take advantage of it."

Be that as it may, today in the USA about 100 couples take a pre–conception test every week, in Spain - about 50. The starting material is a drop of blood or saliva. The cost of the analysis is 560 euros. But the test, of course, does not guarantee the birth of a healthy child: both because it detects only 180 diseases, and there are an order of magnitude more of them, and because dangerous mutations are not only inherited, but also arise directly in the embryo's body. So the birth of a healthy baby was and remains a great success.

Portal "Eternal youth" http://vechnayamolodost.ru23.09.2013