Passage testing before conception of the child
If you are planning a pregnancy, and you have had cases of Down syndrome in your family, you can undergo genetic testing that will help you understand all the issues. This procedure will show whether you or the partner are carriers of a translocation chromosome, which increases the risk of developing a translocation type of Down’s syndrome in the fetus. However, such a test will not reveal the possibility of developing trisomy of Down syndrome, the most common form of this disease.
When you visit a genetic counselor, you will understand why you need to conduct tests, what results mean and how this can affect family relationships.
Screening tests during pregnancy
They do not diagnose the development of Down syndrome in a fetus, but indicate a possible likelihood of such a blemish. The screening tests include:
- Intrauterine ultrasound. He reveals signs of Down’s syndrome development in the first trimester of pregnancy. With its help, you can see excess fluid in the neck of the fetus. Having measured the thickness of the skin fold, the specialist will determine how large the gap between the skin surface and the neck is. This test is not available everywhere, as it can only be carried out by an experienced specialist.
- Test for trivalent or tetravalent vaccination of maternal serum. The first of these tests is performed in the second trimester of pregnancy. With its help, measure the level of such substances in the body:
Alpha-Fetoprotein
Estrogen (estriol)
Human chorion gonadotropin - A four-valent screening test involves conducting a trivalent test and examining a hormone like inhibin A, which is produced by the fetus and the placenta. It allows to detect more cases of Down’s syndrome than a similar trivalent test and practically does not increase the risk of receiving a false positive response. Both procedures are carried out in the second trimester of pregnancy.
Additional procedures that can be performed in the first trimester of pregnancy:
- Combined screening
- Universal screening
When combined screening, check ultrasound, a blood test for the human chorionic gonadotropin level and a blood plasma protein (A), the presence of which is characteristic during pregnancy. According to the reliability, he is equated with quadrivalent screening for the definition of Down syndrome. And the main advantage of this procedure is that it can be done before all other tests.
In general screening, the results of tests of the first and second trimester of pregnancy are used to determine the probability of developing a fetal syndrome in Down’s syndrome. This is one of the most reliable and affordable tests. The answer can be obtained only after a thorough conduct of all the above procedures. Thus, a woman can get a reason for concern already at the initial stage of pregnancy.
To carry out all screening tests, you need to obtain the consent of the future mother. Some women believe that knowing the possibility of complications in advance, they will be able to prepare themselves for this. Others, on the contrary, feel more comfortable, if they remain in ignorance.
In any case, the number and combinations of screening tests that make a pregnant woman completely depend on her preferences and desires. For example, if a woman is concerned about the accuracy of the result and does not want to undergo an amniocentesis, the doctor may advise her to do an intrauterine ultrasound and a blood test in the first trimester, and then a three- or four-valent test in the second.
Diagnosis during pregnancy
Chromosomal analysis, called a karyotype test, can determine the first symptoms of Down’s syndrome during pregnancy. In order to take a sample of the substance from the fetus or from the placenta, one of the following methods is used:
- Amniocentesis. It is usually performed at 15-18 weeks of pregnancy. The amniotic fluid that surrounds the fetus contains cells and other substances that can tell you about the health of the child. The specialist checks their number and size to inform their mother about any deviations in development, if necessary. The test is done by passing a needle through the abdominal cavity into the uterus. For research in the laboratory, approximately 2 tablespoons (30 ml.) Of amniotic fluid are taken. The risk of miscarriage after amniocentesis is 1 of 370 cases. He and 99.8% accurately diagnose Down’s syndrome, the results are reported to parents in a few weeks.
- Chorionic villus biopsy. This test is performed earlier than amniocentesis, usually 10-12 weeks gestation. The chorion nares are small finger-shaped outgrowths that are in the placenta. The genetic material of these villi is identical to that of the fetus. A biopsy of these particles will give genetic information about the fetus from which it can be established whether the child is predisposed to developing pathologies, for example, Down’s syndrome. A sample for research is taken from the woman’s vagina. The doctor passes through a passage between the walls of the vagina a probe with a mirror and uses ultrasound to guide it through the cervix into the placenta. Less commonly, another method is used: the igloo is guided through the abdominal cavity into the uterus. After the device reaches its destination, collection of the sample begins. The probable risk of miscarriage after this test is 1 for 360 cases. The results are known in a few days.
Since these tests carry a portion of the risk, they are not performed as normal procedures, but are recommended for pregnant women who are at risk of developing fetal abnormalities at the chromosome level. This applies to those women who showed abnormalities in the cervical fold of the fetus on ultrasound, a positive result of a three- or four-valent screening test came if the future mother is over 35 years old if the family already has children with Down’s syndrome or had cases of such a disease before.
Only you decide to have the fetus checked for Down syndrome. The earlier you learn about the possible pathologies in the development of a future child, the more time you will have to make a decision about his future fate. For some women, a positive test result means an immediate termination of pregnancy, while others, after receiving such information, begin to prepare themselves morally for the birth of such a baby and think everything over in advance. Sometimes it is useful in this case to seek help from a genetic counselor. If the fetus is diagnosed with Down’s syndrome, the doctor may advise you to undergo ultrasound cardiography, which will show possible heart problems and intrauterine ultrasound to detect abnormalities in the digestive system. All additional concerns about other vices will be considered after the birth of the child.
Diagnosis of the disease after the birth of a child
If Down syndrome is not detected during the test for the detection of a karyotype (using a chorionic villi sampling or amniocentesis), certain physical signs immediately after the birth of the child give the doctor to understand that this is Down’s syndrome. Although the neonate symptoms of the disease may appear blurry, it all depends on the form of the defect. However, a preliminary diagnosis can be made based on checking the physical characteristics and:
- Results of three- or four-valent screening (if they were conducted).
- Studying of median cards of parents.
- Examination of the child for other health problems.
To confirm the diagnosis, the baby can also take a blood test for the presence of abnormalities in the development of chromosomes.
Check at birth and throughout life
Specifically for such patients, members of the American Academy of Pediatricians and members of the medical organization to combat Down’s syndrome developed guidelines for screening tests in each age group. Doctors test patients with Down syndrome for the presence of typical health problems: heart disease, hearing and hearing impairment.
Detection of the disease at an early stage
Your consent to a fetal test for Down’s syndrome may be necessary if:
- You are 35 or more years old.
- At you or the partner there were in a family cases of a similar disease.
- There is information that you or the partner is the carrier of the translocation gene, which causes the development of a certain type of Down’s syndrome.
The procedure that is used to identify Down syndrome is called a test for trivalent vaccination of maternal serum. For a formal diagnosis of this disease, a karyotype test is also used. A sample for it is taken during an amniocentesis or chorionic villus sampling.
If you are planning a pregnancy and want to be aware of a possible risk, consult a geneticist for advice. For example, when a family already has a child with Down’s syndrome, parents can consult and determine the risk of having a second baby with the same blemish.