What are the causes of these pathologies and what is the risk of having a child with trisomy in 21 18 13 chromosome - let's try to figure it out.
Pathophysiology of Diseases
The most common gene pathologies - trisomy on 13, 18, or 21 chromosomes arise as a result of an incorrect distribution of the gene material in the process of cell division. In other words, the fetus inherits from the parents instead of the prescribed two chromosomes, while an extra copy of 13, 18 or 21 chromosomes prevents normal mental and physical development.
According to statistics, trisomy on the 21st chromosome (Down's cider) occurs much more often than trisomy on the 13th and 18th chromosomes. And the life expectancy of babies born with Patau and Edwards syndromes, as a rule, is less than a year. While the carriers of three copies of the 21st chromosome survive to old age.
But in any case, children with similar anomalies can not become full members of society, we can say that they are doomed to loneliness and suffering. Therefore, pregnant women who, after carrying out biochemical screening, found a high risk of trisomy on the 13th, 18th, 21st chromosome, are additionally examined. If the diagnosis is confirmed, they may be asked to terminate the pregnancy.
Trisomy 21 18 13: interpretation of the analyzes
The risk of having a child with trisomy of 21, 18, or 13th chromosome increases at times with the age of the mother, but this can not be excluded from young girls. In order to reduce the number of children born with these pathologies, scientists have developed special diagnostic methods that allow one to suspect that something is wrong during pregnancy.
At the first stage of diagnosis, future mothers, doctors are strongly recommended to pass screening tests, in particular, the so-called triple test. From 15-20 weeks, the woman gives a blood test, according to which the level is determined: AFP (alpha-fetoprotein), estriol, hCG and inhibin-A. The latter are characteristic markers of development and condition of the fetus.
In order to establish the risk of trisomy on the 21, 18, 13 chromosome, the age norms compare the obtained indicators. It is known that women have a risk of developing a fetal Down syndrome:
- under the age of 25 1: 1250;
- in 30 years - 1: 1000;
- in 35 years - 1: 400;
- in 40 years - 1: 100;
- in pregnant women over 45, the risk of pathology at times increases - 1 to 40.
For example, if the screening result of a 38-year-old woman is 1:95, this indicates an increased risk and the need for an additional examination. For the final diagnosis, methods such as chorion biopsy , amniocentesis , cordocentesis, placentocentesis are used.
The dependence of the increase in the risk of having children with trisomy 13, 18, depending on the age of the mother, is also traced, but it is less pronounced than in the case of trisomy 21. In 50%, the deviations are visualized during ultrasound. For an experienced specialist, it is not difficult to determine the Edwards or Patau syndrome by characteristic features.
