Can Down's syndrome be detected by other tests besides Down's syndrome?

Down's syndrome can be detected by other tests besides Down's syndrome.

Specific analysis:

Down's syndrome is the most common prenatal test for Down's syndrome, and there are several other tests besides Down's screening that can also detect Down's syndrome.

Down syndrome screening methods:

1, amniotic fluid cell chromosome examination:

Amniotic fluid cell chromosome examination is an effective method of prenatal diagnosis of Down syndrome, Down's screening results are A pregnant woman with a Down's syndrome screening result of "high risk" needs to be diagnosed as having a child with Down's syndrome. The most commonly used technique for prenatal diagnosis is amniocentesis, in which a needle is inserted into the amniotic fluid through the pregnant woman's abdomen under ultrasound guidance, amniotic fluid is extracted, and fetal cells are analyzed for chromosomes. It is suitable for pregnant women between 16 and 20 weeks of pregnancy. In addition to amniocentesis, techniques to perform prenatal diagnosis include chorionic villus biopsy, fetal umbilical vein puncture, and fetoscopy. The common karyotype is the same as the peripheral blood cell karyotype.

2, fluorescence in situ hybridization:

With the corresponding part of the sequence of chromosome 21 as a probe, and the peripheral blood lymphocytes or amniotic fluid cells for hybridization, the cells of patients with Down's syndrome can be presented with three chromosome 21 fluorescence signal. If the specific sequence of the core region of Down syndrome is selected as a probe for FISH hybridization analysis, the abnormal site of chromosome 21 can be precisely located and the accuracy of detecting chromosome 21 numerical and structural abnormalities can be improved.

3. Other examination methods:

Routine X-ray film, ultrasound, electrocardiogram, electroencephalogram and other examinations. Some children may find congenital heart disease, backward bone age, EEG abnormalities and other changes.

》》》》 Related article: How Down's syndrome is diagnosed

Down's syndrome screening risk rate mainly means that the results of the Down's syndrome screening test are inaccurate.

Specific analysis:

Down's syndrome screening is generally done through the maternal serum concentration of alpha-fetal palmitate (AFP), beta chorionic gonadotropin (β-HCG) concentration, the results of free estriol, combined with the age of the pregnant woman, her body weight, her maternal history, and the week of gestation, to calculate the risk factor for the corresponding disease. The result is a risk value, e.g. 1:2000, which indicates a 1 in 2000 chance of developing the disease. Depending on the software system used, the parameters entered into the analysis vary slightly, and some software also includes fetal nuchal colloid thickness in the calculation, so the reference risk coefficients vary from unit to unit.

Screening results are subject to a certain amount of error, i.e., false negatives and false positives, regardless of whether they are in the high-risk group or the low-risk group.

1. False positive is when the report shows an abnormality and the fetus is normal and false negative is when the report is normal and the fetus is sick. To do amniocentesis or not to do amniocentesis, you have to analyze the specific problem.

2. In principle, after eliminating the interfering factors (generally more common is the error of gestational week), it is recommended to do the diagnosis, i.e., amniotic fluid fetal cell chromosome analysis. If it is a low risk, continue the pregnancy check.

3, gestational week error is mainly for some irregular menstrual cycle or longer cycle (more than 37 days) pregnant women, correct the gestational week and then analyze, to rule out the misjudgment caused by gestational week error.

4, Down syndrome is the most common chromosomal disease, the incidence rate of 1.5 per thousand live births, its main features for mental retardation, congenital multiple malformations, growth retardation, so far there is no effective means of treatment.

Down syndrome risk rate does not confirm the diagnosis of Down's syndrome:

In foreign countries, over the age of 35 years of age of mothers are routinely do amniocentesis, although the puncture there is a little bit of risk, such as: caused by infection, bleeding, miscarriage, etc., but the incidence of very low, weighing the pros and cons of high-risk mothers-to-be or should be done to confirm the diagnosis of amniocentesis.

The Down syndrome risk rate threshold is 1/270, which is greater than high risk and less than low risk.

A high risk of Down syndrome is a high risk of having a baby with Down syndrome after Down's syndrome screening.

Reason:

Because a high risk for Down syndrome is only an estimated risk factor based on the mother's blood test, and then based on the mother's age, weight, and so on, a fetus with a high risk for Down syndrome doesn't have to be a Downs baby.

Pregnant mothers who are at "high risk" for Down syndrome need to be diagnosed with a child with Down syndrome.

Specific methods:

1, the current prenatal diagnosis of the most commonly used technology is the amniocentesis technology, that is, under the guidance of the ultrasound, the needle through the abdomen of the pregnant woman into the amniotic fluid, the amniotic fluid is extracted, and the chromosome analysis of fetal cells.

2. Amniocentesis is suitable for pregnant women who are 16 to 20 weeks pregnant. Some pregnant women or their families may have doubts about the safety of amniocentesis, but according to statistics, the miscarriage rate caused by this technique is only 0.5%.

3, in addition to amniocentesis, prenatal diagnostic techniques include chorionic villus biopsy, fetal umbilical vein puncture, fetoscopy and so on.

There is no effective treatment. The best means is to terminate the pregnancy before the mother gives birth.

Prenatal prevention for pregnant women is as follows:

1. Genetic counseling

The older the pregnant woman, the higher the risk rate. The risk of recurrence for standard Down syndrome is 1%. Both parents of a child with a translocation should be karyotyped to detect balanced translocation carriers: if the mother has a D/G translocation, there is a 10% risk rate for each child; if the father has a D/G translocation, the risk rate is 4%. The vast majority of cases of G/G translocation are disseminated, with most parents having a normal karyotype, but carriers of the 21/21 translocation have been found to develop the disease in 100% of their offspring.

2, prenatal diagnosis

is an effective measure to prevent the birth of children with Down syndrome. Couples who have a history of the disease should have a prenatal diagnosis when they have another child, that is, chromosomal karyotyping, sampling includes mid-pregnancy amniocentesis for amniotic fluid cells, mid-pregnancy embryonic chorionic villus cells and mid-pregnancy umbilical cord blood lymphocytes and other analyses. Prenatal screening serum markers HCG, AFP determination has a certain clinical significance, because it can reduce the amniocentesis for prenatal diagnosis of blindness, suggesting the existence of high-risk groups of pregnant women, so that these pregnant women are able to make further prenatal checkups and counseling, to maximize the prevention of the birth of children with Down syndrome.