When Down’s syndrome is detected in a baby at birth, the parents experience serious psychological trauma. Of course, similar health difficulties can happen to anyone, but they can be prevented. Especially when modern diagnostic methods have already reached their heights.
For a very long time, the only way to diagnose this hereditary disease before the baby was born was to study the amniotic fluid obtained with the help of amniocentosis. Thanks to this technique, it is possible to obtain amniotic fluid using a thin needle through an insignificant puncture in the abdomen of the pregnant woman. But due to certain features, this technique is not recommended for examining all expectant mothers. Therefore, only those women who are at risk, for example, late pregnancy, can undergo this procedure.
Modern methods of detecting Down syndrome
Such horror as having children with Down syndrome can happen to every couple. Even a 25-year-old expectant mother can have a child with this terrible diagnosis. Her chances are reduced to 1 in 1250. Total screening of pregnant women is carried out according to the developed method of non-invasive antenatal diagnosis. This procedure is indicated only for those women who are at risk, in particular, late pregnancy. This method is based on the detection of various biochemical markers in the venous blood of a pregnant woman.
The most promising diagnostic technique at an early stage is ultrasound examination of the thickness of the collar zone of the fetus. If he has Down syndrome, subcutaneous fluid collects on the back of his neck between the 11th and 13th week. But to use this method, it is required to carry out its expert assessment and equipment, which is rather rare even today. The probability of a false positive result, according to the NSC, is 20%. The use of this method as an independent research method is not yet expected.
The most effective way to detect Down syndrome is a combined technique. It means ultrasound of the thickness of the collar zone and the detection of all kinds of biochemical markers in the blood serum. In the period from the 10th to the 13th week, specialists determine markers that are associated with pregnancy – these are plasma protein A and the free-subunit of human chorion. After 14 weeks of pregnancy, at about 16-18 weeks, a “triple test” is performed: the concentration of the female sex hormone is investigated – free estriol uE3, serum alpha-protein AFP, human chorionic gonadotropin b-hCG (total hCG or free hCG-subunit). This method showed only 1% of false positives. In all other cases of amniotic fluid examination, the diagnosis of Down syndrome was confirmed. With a decrease in the number of studies, the effectiveness of the method also deteriorated. In particular, if only the traditional “triple test” is carried out – AFP, uE3 and b-hCG in the period from the 14th to the 20th week of pregnancy, then an erroneous result was observed in 9.3% of cases. The detection of only AFP (alpha-fetoprotein) in the blood serum is not even considered, since it is not suitable for making this diagnosis.
The National Screening Committee has set the following requirements for the method of antenatal diagnosis of Down’s syndrome: the screening method is satisfactory, the positive results of which are 75%, false positives are not more than 3%. For pregnant women with a high risk of having a baby with Down syndrome, it is recommended to undergo an invasive study (amniocentesis, biopsy, etc.) to make a final and accurate diagnosis.
Down syndrome causes
If you look, then the reasons for the formation of Down syndrome should be sought in the intrauterine development of a chromosomal abnormality of the fetus, which is characterized by the appearance of an additional copy of the genetic material – the 21st chromosome, or the entire chromosome (trisomy) or its specific part due to translocation. For a normal karyotype of a healthy person, 46 chromosomes are characteristic, and in the presence of Down syndrome, the karyotype is formed from 47 chromosomes.
Scientists note that the reasons for the development of this syndrome are in no way connected with external factors, parental behavior, the use of some medications and other negative factors. They are caused only by chromosomal events that cannot be prevented or changed in the future.
Down syndrome signs
The symptoms of Down’s syndrome are immediately apparent at birth. This is indicated by the small size of the head and the shortened skull; ears of an irregular shape and a flattened face; saddle nose and flat nose; small mouth and chin; open mouth and thick tongue; slanting eye section and folds in the inner corner of the eye; shortened neck and folds on it; short arms, legs and fingers; flat wide palms and a horizontal fold on them; concave pinky and large toes; weak muscle tone.
At the birth of a child with this syndrome, almost all of the listed external signs will be determined. Confirmation of the diagnosis is the result of a genetic test for the karyotype.