Down Syndrome Analysis

Down syndrome is a fairly common disease associated with changes in the number of chromosomes. Therefore, to identify this disease, as well as other developmental anomalies, it is recommended that pregnant women be given appropriate tests, especially if the woman is over thirty-five years old. This is due to the fact that with age in women the probability of a baby with this disease increases.

There are two types of studies: diagnostic tests and a screening test. The first type of study yields an accurate result( eg, amniocentesis or chorionic villus sampling), but there is an insignificant risk of miscarriage. The second type of study is less precise, but more secure.

Types of screen tests

There are several similar tests, but not all tests are available in our country or in any particular region. If a woman wants to do a certain kind of test, but does not do it in a hospital at the place of residence, then she can spend it in a paid clinic. It should be borne in mind that a blood test and ultrasound are all screening tests that can not absolutely accurately tell if a baby is healthy or not, but they allow you to determine whether a diagnostic test should be done.

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Screening test in the period I trimester

Between the eleventh and fourteenth weeks of pregnancy, a woman undergoes ultrasound, which determines the thickness of the collar space. The doctor measures the subcutaneous fluid on the surface of the fetal neck. This test is necessary in order to determine the likelihood of Down syndrome.

In addition, there is a blood test, which can be handled together with ultrasound, in this case will result in a so-called double test.

Blood analysis can determine:

  • level of PAPP-A protein( plasma protein);
  • level of human chorionic gonadotropin( otherwise, beta-hCG);

If the baby has Down syndrome, then the level of these substances will differ from the norm.

These tests are very accurate individually, but the accuracy is greatly improved if they are carried out at the same time. Ultrasound reveals about seventy-five to eighty-two percent of the births of children with the syndrome, and blood analysis reveals about sixty to seventy percent of these children. At simultaneous carrying out of these researches the probability of revealing a syndrome makes from ninety to ninety three percent. False detection of the disease occurs in three to five percent of cases.

However, the accuracy of a double test, in any case, depends on several factors, including the scanner, the professionalism of the doctor conducting ultrasound. In addition, the test result is affected by the time period between the two procedures.

Screening test during the period of the 2nd trimester

This test consists of a blood test, which must be performed for a period of fourteen to sixteen weeks. This analysis allows you to know the level of some indicators, including:

  • estriol;
  • beta-hCG;
  • inhibin A;
  • AFP( otherwise, alpha-fetoprotein).

In the presence of Down's syndrome in a child, the level of the second and third index in the blood is increased, and the first and fourth, on the contrary, are lowered.

In general, there are several types of tests: double( with the level of extriols and beta-hCG), triple( to determine the level of extriol, alpha-fetoprotein and beta-hCG), and quadruple( determine the concentration of all four indicators).

Combined screening test for I and II trimester

This combined test combines the results of a blood test with plasma protein and beta-hCG levels at the eleventh to fourteenth week of pregnancy and the estriol, AFP, and inhibin A assay conducted atSixteenth-eighteenth week of pregnancy. This test takes into account the results of the first and second trimester studies and shows the probability of identifying the syndrome at ninety-four percent. At the same time, false detection occurs in five cases out of a hundred.

Unfortunately, such highly informative tests are not available in every region of the country. This test takes into account many indicators, and therefore the results can be learned only in the second trimester.