Down syndrome is called fairly common genetic disorder for which is primarily characterized by the lag in mental and physical development. In 1866, a British doctor, John Langdon Down first described the symptoms of patients exposed to the disease. That's his name called syndrome. However, the cause of this genetic abnormality have been identified only in the middle of the twentieth century French geneticist Lejeune.
Causes of Down Syndrome
This abnormality, like Down syndrome, is associated with the violation in the set of chromosomes, and is characterized as having an extra 47th chromosome karyotype, while the norm is number 46. This is manifested in disorders of mental and physical development of man. It should be said that one child out of 600-700 newborns exposed to the disease, regardless of ethnicity. This anomaly occurs with equal frequency among both sexes.
As already noted, the causes of Down syndrome were established relatively recently, although the opinions of experts in the field disagree on this issue so far. The main factors that affect the likelihood of disease in children:
- Age of parents;
- Closely marriages;
- Age child's grandmother on his mother's side.
The first cause of Down syndrome, medical supervision, performs maternal age of the child. It is known that the probability of conceiving a child with this disorder at the age of women from 25 to 30 years is 1 in 1000 from 35 to 40 - 1 to 200, and after 45 years - 1 to 20. So far, the experts can not fully explain the relationship between the syndrome and maternal age. Some of them believe that it is caused by disorders that occur during the second meiotic division, is already happening in adult women. Also found that the age of the father of the child plays an important role, especially if it is 42.
Closely marriages are the least common cause of Down syndrome in the civilized world. However, the most interesting from the scientific point of view factor is the relationship between the disease and the age of the grandmother of the mother of the child. Studies have shown that the older was a grandmother when her daughter gave birth, the greater the likelihood that her baby daughter born with this pathology.
This fact is explained as follows. Even in the womb, the female embryo is in the process of the first meiotic division during which chromosome segregation occurs. Substances that come from the mother to the fetus during this period, can also have an impact on the development of their reproductive cells. Female children are born with a set of future ova, which have already passed the first meiotic division. It is among this set of definitions of the eggs has an extra chromosome, and if one of them will be fertilized later, the baby will be born with Down syndrome. Thus, it is believed that the number of such cells in the ovaries of the newborn is directly dependent on the age of its mother.
Symptoms of Down syndrome
Today, a woman during pregnancy can pass some tests to determine if a fetus of this genetic abnormality. It is known that they are the cause of reducing the number of sick children in recent years, as many women in the state, found violations, to terminate their pregnancies.
If the child is born, it is the presence of the disease may indicate a number of characteristic external signs of Down syndrome:
- The plane of the face and neck;
- Shorter skull;
- Short arms and legs;
- Short fingers;
- Skin folds covering the corner of the eye;
- A fold of skin on the neck.
These are the most common signs of Down syndrome that are observed in 70-90% of cases. At the same time, there are others that are less common, but are also characteristic of the disease. Among them should be mentioned:
- The plane nose and nose;
- Wide and short neck;
- The curvature of the little finger;
- Cataract development after the age of eight;
- The anomalies of the teeth;
- Open mouth;
- Arched palate.
Furthermore, during development of Down syndrome may be mentioned pathologies such as hypotonia, chest deformity, strabismus, congenital heart disease, and leukemia.
Diagnosis of Down Syndrome
In order to detect the development of Down syndrome, there are some basic methods of diagnosis. The first is the ultrasound study. In the first trimester of pregnancy a woman can pass the test for measurement of fetal nuchal translucency. If the results of a test conducted by a vaginal probe, its thickness is more than 2, 5 mm, it is possible to speak about the presence of the disease in the unborn child. If the study was carried out through the front wall of the abdomen, then the presence of disease in the fetus says index of 3 mm. In addition, it is possible to conduct ultrasound for the presence of the nasal bone: the development of Down syndrome in the fetus she is either very small or non-existent.
Another common method of diagnosis in this case is double the biochemical analysis of blood on 10-13 th week of pregnancy and a triple - on the 16-18 th week. Once the results are obtained and ultrasound tests for accurate diagnosis of Down syndrome can go horionbiopsiyu or amniocentesis, which most accurately detect the presence of genetic abnormalities of the fetus. Horionbiopsiya involves analyzing tissue membrane of the embryo, and amniocentesis is a puncture of the front wall of the mother's abdomen with the aim of taking to analyze fetal tissue or amniotic fluid.
It should be noted that these procedures carry a greater danger for the health of the expectant mother and the child. In a survey of possible damage to the internal organs of a woman, bleeding, injury of the fetus, as well as the threat of termination of pregnancy.
It is important to add that the Down syndrome until recently was considered an incurable disease. However, recently in the United States it was an experiment that gives comforting forecasts. The study has found the ability to lock an extra chromosome in the karyotype, influence the development of disease.