Identification of down syndrome during pregnancy. Analysis for Down syndrome - why is it needed, how to pass, decoding
Now all pregnant women, among other numerous tests, are recommended to undergo a screening test to identify a risk group for giving birth to a child with Down syndrome and some other types of congenital malformations of the fetus. At the same time, they always talk about the need to take an analysis (how, after all, such a serious analysis, for genetic diseases, must be done!), But doctors in antenatal clinics almost always (with extremely rare exceptions) “forget” to tell about the further development of events. Or they don't think it's necessary. But it would be worth it ... This analysis should not fit into the general series of tests prescribed during pregnancy. It is necessary to give detailed information about these tests and, in particular, about further studies that are prescribed if they are at risk, so that women can consciously choose whether they want to take this test.
First, let me tell you my story. For clarity, when I was pregnant with my youngest daughter, I didn’t get registered with the district antenatal clinic and didn’t intend to take all the insane bunch of tests that are now prescribed to pregnant women. I was going to pass only the main ones, at first I was observed simply by a gynecologist I knew. And the doctor whom I trust (a very good person, but, unfortunately, brought up by the system), said that it is imperative to pass this very screening test. Well, I went through it. As expected, an ultrasound at 10 weeks, then immediately a blood test. After 2 weeks, the result comes - THRESHOLD risk of having a baby with Down Syndrome ... Of course, I tensed up. The doctor says - take it again at 16 weeks. I did another ultrasound - on the ultrasound, it seems, everything is in order. I retake blood, two weeks waiting for the result. The result comes - HIGH RISK. I don’t remember exactly the ratio, unfortunately, but they send me to some special center where they do all this. I decided to start by studying in detail all the information about these tests. And here's what I found out: according to the combined screening - ultrasound + blood test for AFP and hCG - one can only ASSUME the presence of such a deviation in the fetus. The diagnosis can be made (and even then not 100% ...) exclusively with the help of invasive methods of prenatal diagnosis - chorionic villus biopsy and amniocentesis (examination of amniotic fluid, which is taken directly from the fetal bladder with a special needle). And such methods are associated with the risk of a number of pregnancy complications: miscarriage, the development of a conflict according to the Rh factor and blood type, infection of the fetus, the development of hearing loss in a child, etc. In particular, the risk of miscarriage after such studies is 1:200, and according to some data and above. In addition, when diagnosing a malformation, treatment is impossible, and the woman simply faces a choice - either to leave the child (why then was it necessary to take an analysis? ...) or have an abortion. Taking into account the fact that I received repeated tests at 18 weeks, if not later, then even if I had gone for an amniocentesis, the diagnosis would have been by no means earlier than 20 weeks, and possibly even later. And this is already a full 5 months, when an abortion is already very dangerous for health. And I absolutely understood that I would not do an amniocentesis in any case, for a number of reasons - firstly, the idea of putting a possibly perfectly healthy child at great risk horrified me and continues to terrify me. Secondly, I would not have an abortion anyway, especially at such a time. Therefore, at the family council, we decided that we forget this whole story and are expecting a healthy child. I pulled myself together, tuned in the right way. But the worm was still sitting inside, whatever one may say ... And the thoughts about it still remained on the subconscious mind, and this, believe me, does not give much emotional calm. So it turns out: why, in fact, was it necessary to take an analysis? To tickle your nerves???
Fortunately, my Svetka was born healthy, to the delight of everyone. But if I happen to get pregnant for the third time, under no circumstances will I do a screening. By the way, when I later called the doctor, who advised me to get tested, she told me, “What a clever girl you are, that you didn’t go for an amniocentesis and decided to give birth! I have one girl done here, infection occurred, and as a result she lost a healthy child ... "
Such is the story. And now let's stop more details on the research itself.So, a complete combined screening of the I - II trimester of pregnancyperformed to identify the following congenital malformations in the fetus:
Down syndrome (trisomy of the twenty-first pair of chromosomes) Edwards syndrome (trisomy eighteenth pair) Neural tube defects (spina bifida and anencephaly) (16-18 weeks only)The test includes:
Ultrasound examination at 10-13 weeks of pregnancy (by date of menstruation)In the first trimester, the main dimensions for calculating risks are the width of the cervical transparency (wtranslucency - this is what the accumulation of subcutaneous fluid on the back of the neck of the fetus in the first trimester of pregnancy looks like on ultrasound) and the definition of the nasal bone (inlate first trimester nasal bone not defined by ultrasound in 60–70% of fetuses with Down syndrome and only 2% of healthy fetuses). By the way, I would like to note that ultrasound can reliably determine whether the fetus has problems, and a three-dimensional ultrasound for a period of 4-5 months of pregnancy, made by a good specialist, further increases the accuracy.
2. Blood test for hCG (chorionic gonadotropin) at 10-13 weeks and for AFP (Alpha-feto-protein) at 16-18 weeks.
AFP is a substance that is synthesized by the baby's liver and passed into the amniotic fluid and from there into the mother's blood. AFP concentration continuously rises, reaching a maximum at about 30 weeks. From 16 to 18 weeks, the gap between normal, low (in Down's syndrome) and high (in neural tube defects) AFP levels is especially large. However, there is no level that would clearly define the pathology of the child. The level of AFP depends very much on many factors, for example, you need to know the gestational age very accurately, smoking affects it, and many other factors, and it can be high or low without any fetal pathology.
Recently, more and more women, according to the results of a blood test, fall into a high-risk group for giving birth to a child with Down syndrome. Moreover, these are young girls in whom ultrasound did not reveal any abnormalities. We will not discuss why this happens, although the author of the article has his own thoughts on this matter ... But in the vast majority of cases, if a woman decides not to do further research and give birth, a healthy child is born. Only the whole pregnancy proceeds with a constant question in my head ...
In fact, according to statistics, children with Down syndrome are born on average in one case out of 600-800. At the same time, for a mother under the age of 30 without genetic diseases in the family, the risk of having such a child is very low (for example, at 20 years old - 1 in 2000 newborns). The risk increases after age 35, and at age 40, statistically speaking, the probability of having such a child is approximately 1:110. However, this is still less than 1%.
It is important to note that approximately half of all cases of chromosomal abnormalities, including Down syndrome, end in a natural miscarriage at an early stage of pregnancy (up to 6-8 weeks).
If a high risk is detected according to the results of the tests, the woman is offered to do an amniocentesis - the collection of amniotic fluid from the fetal bladder. It is done no earlier than 18 weeks, since before this period there is not enough amniotic fluid. The results of the analysis are usually ready in another 2-3 weeks, that is, a more or less reliable conclusion can be obtained only by the end of the fifth month of pregnancy. Since treatment is impossible, the woman is offered to have an abortion. This late termination of pregnancy has very severe physical and emotional consequences. At this time, the woman's body will respond to an abortion as a premature birth of a child, up to the release of milk from the breast.
In addition, amniocentesis carries the following risks:
1) spontaneous abortion with the loss of a healthy child, which occurs in about 1.5% of cases. This risk is increased if there are fibroids or fibroids in the uterus. If a woman has had a miscarriage in the past, the risk also increases.
2) One in 200 women suffer from infectious and other complications
3) In some cases, damage to the fetal bladder is noted, and the woman must be in the hospital for several days to several months.
4) If the mother is Rh negative, the doctor will give a special injection, and in some cases the injection itself will cause a miscarriage.
5) In about 5% of cases, doctors fail to get an effective analysis and the mother still remains in the dark
6) Most women experience contractions for several hours during and after the procedure.
And the main thing to remember is that amniocentesis does not correct developmental disorders. It only gives information about the person who already lives in the mother's belly. And the woman is faced with a choice: whether to accept this man or take his life.
Therefore, before undergoing a screening test, seriously consider - if you are at risk, whether you are ready to take the risk of an amniocentesis, and if the diagnosis is confirmed, whether you will decide on a late-term abortion. And think about what is more terrible for you - to kill a healthy child, whose movements the mother already feels at this time, or to give birth to a downer...
Today, doctors strongly recommend that absolutely every expectant mother undergo a genetic risk test. The mandatory list of examinations for genetic pathologies includes an analysis of Down during pregnancy. Someone immediately and unconditionally agrees to undergo such a diagnosis, while someone believes that it is better not to know anything at all for the time being.
This approach has serious consequences in the future. After all, it is very important to understand that a child born with Down syndrome lags behind in mental and physical development, from the moment of birth, he is diagnosed with serious diseases, often incompatible with life. In society, such a child, with rare exceptions, is considered a black sheep.
If more recently, an analysis for Down's syndrome was prescribed to a woman who has reached the age of 35, or parents over the age of 45, now this examination is mandatory for everyone. Down syndrome is getting younger, and there are no guarantees that healthy, prosperous and young parents will not have a baby with one extra chromosome. Unfortunately, such a diagnosis often leads to termination of pregnancy according to indications.
What is Down Syndrome
Nature is very wise to work on every new person. When laying the genetic scheme, it is assumed that the future baby has 46 chromosomes - 23 of them were inherited from the mother and the same number from the father. Often there is a doubling of one chromosome from 21 pairs. And then instead of the prescribed 46 chromosomes, it becomes 47. This is evidence of the alleged Down syndrome.
The studied pathology has no continental and racial advantages. Absolutely everyone can fall into the risk zone. However, doctors have identified a number of factors that provoke the birth of children with Down syndrome:
- the age of the future mother and father is 35+;
- the baby's parents are blood relatives;
- often physicians include the age of the grandmother as a risk factor. The later the grandmother gave birth to the mother, the higher the risk of having a grandson with a pathology in the chromosome set.
- parents - owners of a hidden mutation of chromosome 21. One of its sections sticks to chromosome 14 and coexists with it. Outwardly, it has no signs. Scientists call this phenomenon “familial Down syndrome.”
Scientists have proven that neither ecology, nor nutrition, nor the lifestyle of future parents can reduce or increase the risk of having a sick child. This is an anomaly that occurs at the chromosomal level. It cannot be prevented or somehow prevented.
Children born with Down syndrome are very weak. It is not uncommon for such an infant not to live up to a year. Numerous malformations of all organs, weak immunity, special functioning of the nervous system, lesions of the brain - all these are the consequences of the appearance of one extra chromosome.
It is important for a woman who has been given this terrible diagnosis to know that with proper care and boundless love, “sunny” children can live perfectly, go to school, and play sports. This requires great moral and physical strength on the part of the parents.
Methods for diagnosing Down syndrome in pregnant women
To date, the most informative way to examine pregnant women for chromosome pathology is screening. This is a set of studies that can identify genetic-chromosomal abnormalities. In addition to Down syndrome, such a diagnosis can notice Edwards syndrome, Patau syndrome, congenital defects of the neural tube in time.
In the first and second half of pregnancy, diagnostics is mandatory, consisting of a biochemical blood test and ultrasound.
Ultrasonography
In the first trimester is assigned from 11 to 13 weeks.
When diagnosing, the uzist draws attention to the following points:
| Indicators | Deviations from the norm |
| nose bones | Shorter than in a normally developing fetus, or absent altogether. |
| Neck width | More than 3 mm. Norm 2 mm. Increased space between the neck bone and the skin. It collects liquid. |
| Shoulder and thigh bones | Shorter than normal |
| state of the brain | The presence of cysts, a violation of the movement of venous blood flows |
| Iliac pelvic bones | Short, obvious increase in angle |
| The size of the fetus from the crown to the coccyx | Less than 45.85mm. |
| Heart condition | Pathology of the development of the muscles of the heart |
Even if a preliminary disappointing diagnosis was made on an ultrasound examination, you should not panic. It can be considered accurate only when several features are combined at once.
Blood chemistry
A blood test taken from a future mother for Down syndrome, combined with ultrasound results, can significantly clarify the picture and identify genetic abnormalities.
In the 1st trimester, inclusive, through the 13th week, a “double test” is taken, that is, the risk of an extra chromosome is diagnosed by two markers:
- Human chorionic gonadotropin (hCG) is a hormone protein produced by the shell of the embryo.
- Specific plasma protein PAPP-A
The reliability of such studies is 85%.
Blood is donated on the same day as the ultrasound examination, on an empty stomach. If the mother is not feeling well, she is allowed to drink some plain water before the examination.
In the second trimester from 15 to 18 weeks, the screening is repeated. In this case, the test is called a "triple test". The level of three proteins and hormones is determined at once:
- alpha - fetoprotein - a protein produced by the fetus and entering the mother's blood;
- free estriol.
Deciphering the results of a blood test for Down syndrome should be carried out during pregnancy as carefully as possible. Incorrect interpretation leads to a false diagnosis, which can lead to irreparable consequences.
A medical error is a common thing in modern reality. The gynecologist is obliged to study the results of both screenings and only then add the woman to the risk group.
All these research methods do not detect a specific pathology, but reveal the degree of risk of its occurrence. The risk can be low with a score of 0.1-1% and high with a score of 1% or more. All these are average figures.
With an average and high level of risk, a control expert ultrasound is prescribed, where an experienced doctor will thoroughly assess the condition of the fetus.
Amniocentesis
When standard diagnostics do not give a clear picture of the course of pregnancy, the expectant mother may be prescribed tests related to taking amniotic fluid. This test is called amniocentesis.
Amniotic fluid is taken under the control of an ultrasound machine with a special needle through the abdomen or vaginal opening.
It is advisable to carry out such a diagnosis after the 18th week of pregnancy, since it is at this time that the required amount of amniotic fluid becomes.
Amniocentesis is carried out strictly according to indications, as it is not a completely safe way to detect chromosomal pathologies.
This examination technique is not suitable for a certain category of women:
- there is a threat of spontaneous abortion;
- placenta on the anterior wall;
- disorders in the development of the uterus;
- chronic diseases of the mother.
Non-invasive prenatal diagnosis of aneuploidy by maternal blood
Today, the safest and most informative way to diagnose and detect fetal chromosomal pathologies without getting into the fragile relationship between mother and unborn baby.
Fetal DNA is isolated from the mother's blood and examined for pathological disorders in the chromosome set.
Efficiency reaches 97%. At the same time, Patau syndrome is detected on the 13th pair of chromosomes, Edwards syndrome on the 18th, and Down syndrome on the 21st.
Identification of Down syndrome in a newborn
Children born with Down's chromosomal pathology have a number of specific external signs:
The special appearance of such children is laid down by a chromosomal anomaly, therefore, Down's babies do not look like any of their parents.
The decision to pass or not to be screened for Down syndrome during pregnancy remains with the woman alone. Physicians can only advise and recommend. So, if at the first screening, a preliminary diagnosis is revealed, and the woman remains firm in her intention to give birth to such a baby, then it is not worth taking risks and undergoing more serious studies.
It is a completely different matter when the expectant mother is not ready to raise a child with Down syndrome. Then the need for unsafe tests to detect pathology is obvious.
It is important to remember that even in the worst cases, there is a way out. There is always a chance to give birth to a healthy and strong baby. But if, nevertheless, a “sunny” child is sent to you, you need to endlessly love and care for him.
Signs of Down syndrome during pregnancy began to be distinguished relatively recently. The pathology was identified by the English physician and scientist John Langdon Down in 1886. According to statistics, 1 out of 700 babies is born with an extra chromosome, which is a determining factor for congenital malformation.
Causes and risks of the formation of abnormal development
In a person with normal development, 46 chromosomes are present, with abnormal intrauterine formation, a karyotype formed from 47 chromosomes is observed, which is a determining factor for Down syndrome.The reasons for the appearance of pathology are not yet fully known to science. Experts say that development is not affected in any way by the environment, the use of potent drugs, or the asocial behavior of parents. Also, the formation of the disease cannot be influenced or corrected.
It is definitely known that the age category of parents affects Down's disease:
- up to 25 years of age, the risk of developing pathology is 1/1560;
- up to 35 years old - 1/1000;
- up to 40 years - 1/215;
- from 45 years old - 1/19.
How to identify Down syndrome during pregnancy?
Signs of down syndrome during pregnancy can be seen already at the first screening ultrasound, for a period from the 10th to the 14th week of gestation. At the same time, the probability of error is quite high when compared with laboratory studies. Therefore, a pregnant woman is offered to take additional tests to recognize the symptoms:- Ultrasound determination of the thickness of the collar space, which is located between the folds of tissues on the neck. This is the main and clear sign of the disease, exceeding the 3 mm threshold.
- A biochemical blood test shows the level of the β-subunit of the pregnancy hormone or hCG - human chorionic gonadotropin. The marker will be caused by an increased index of more than 2 MoM, which often indicates chromosomal abnormalities.
- The study of blood plasma often shows reduced parameters of protein A or PAPP-A - less than 0.5 MoM.
Down syndrome is determined only by the combination of these three markers, while the probability is no more than 80%. Since there is an error that takes into account the human factor and violation of the measurement technique.
Diagnosis of Down syndrome in the second trimester
If the diagnosis of the first trimester showed that there is a high risk of developing an embryo with an extra chromosome, then in the next three months, repeated studies with additional invasive diagnostic methods are recommended. So, in order to determine the down syndrome during pregnancy, the following activities are carried out in the second trimester:- On ultrasound, in 60% of cases, the nasal bone in the fetus is absent, signs of heart disease appear, the humeral and femoral tubular bones are quite short, and abnormal echogenicity of the intestine is determined. In general, the baby is smaller, with a rapid heartbeat and an enlarged bladder.
- A blood test shows an increase in hCG and inhibin A to 2 MoM and above, and the level of a-fetoprotein and free estriol is less than 0.5 MoM.
- Amniocentesis is the sampling of amniotic fluid and the determination of the chromosome set in the laboratory;
- Chorionic biopsy involves the study of placental tissue. Such an analysis is the most revealing, but it is also associated with high risks for the fetus.
- Cordocentesis is performed to examine cord blood and then test for the presence of an extra chromosome.
After labor and the appearance of the baby, the signs of Down syndrome are quite easy to recognize. The disease is identified by a shortened and slightly concave facial skull, irregularly shaped ears, a flat bridge of the nose, and an oblique incision of the eye sockets. There is a thick tongue, a small mouth that is constantly open, a short neck and a poorly developed muscular frame. In addition, a genetic analysis of the karyotype is performed on the newborn, which confirms the diagnosis that a special baby was born.
Today on the site for moms, the site we are considering a serious issue - Why do expectant mothers need screening for Down syndrome? Learn about the details of this procedure.
Some statistics
Unfortunately, Down's Syndrome one of the most common chromosomal disorders, therefore, expectant mothers are recommended to do a test to determine malformations in the development of the fetus.
Today, more and more pregnant women are screened positive for Down syndrome and are in a high-risk group for having a baby with Down syndrome on blood tests. At the same time, many of them are young girls who have no abnormalities on ultrasound.
However, the vast majority of women, if they do not dare to conduct further research, give birth to healthy children. But pregnancy still proceeds under an alarming question mark.
According to statistics, children with Down syndrome appear on average only once in 600-800 cases. Moreover, for a mother under 30 years old and without genetic diseases in the family, the risks of having such children are very small (at 20 years old - one in 2000 newborns). Risk increases after age 35, and at 40 the probability of the birth of such a child is approximately 1:110.
It should be noted that about half of all cases of chromosomal abnormalities, including Down syndrome, end in natural miscarriages in early pregnancy (up to 8 weeks).
What are the screening tests
There are many different screening tests, but not every screening for Down syndrome is available in our country or in certain parts of it. If the test you have chosen is not performed at a clinic in your area, you can have it done for a fee where possible.
The site reminds blood test, ultrasound, or a combination of these procedures are screening tests. They will not give a 100% guarantee of the birth of a healthy baby or with Down syndrome, but conducting such a test helps determine the need for diagnostic tests.
In hospitals, when prescribing a diagnostic test, it is usually from the minimum share of probability. Some believe that this minimum proportion equates to 1 in 150, and others - 1 in 250. That is, the chance that you will give birth to a baby with Down syndrome is 1 in 150 or 1 in 250. Regardless of the indicators that are accepted in your hospital , if you are at lower risk, the results of screening for Down syndrome will be considered negative. This means your baby is unlikely to be born with Down syndrome.
The test detects pregnancy with a risk of chromosomal abnormality. But he also reveals that pregnancy, where there is no threat in the development of Down syndrome. The result of such a test is called false positive.
Screening for Down syndrome in the first and second trimesters of pregnancy
In the period from 11 to 14 weeks of pregnancy, Ultrasound to calculate the thickness of the fetal collar space. There is also a blood test - it is often done in combination with the above ultrasound (the so-called double test). From the blood test, the level of beta-hCG is detected, as well as the amount of PAPP-A protein.
A woman wearing has a different level from the norm. These tests are very accurate, but their accuracy increases if they are carried out simultaneously. Then the probability of detecting a malformation in a child is 90-93 % .
Of course, the accuracy of the double test also depends on various factors (doctor's qualifications, scanner operation, time gap in these procedures).
Its advantages:
- The degree of accuracy is quite high
- There is time to think about what to do if a high risk of Down syndrome is found, screening is designed for this. You can do nothing, but you can conduct a diagnostic test
- A diagnostic test early in pregnancy, such as an amniocentesis or chorionic villus sampling, provides more information.
Flaw:
- A study to determine the thickness of the collar space, however, like a double test, due to high prices and the lack of the necessary materials, is not done in every regional hospital.
In the second trimester, prenatal screening for Down syndrome is based on blood test. It is carried out at 16-18 weeks, determining the level of certain blood parameters.
There are several types of tests:
- Double (detects the content of estriol and beta-hCG).
- Triple (detects the content of estriol, AFP and beta-hCG).
- Quadruple (detects the content of estriol, AFP, inhibin A and beta-hCG).
Its advantages:
- It is not difficult to take a blood test.
- Blood tests are done in many laboratories.
Flaws:
- Accuracy will be lower than in the first trimester. Thanks to the double test, 59% of cases are detected, and the quadruple test reveals 76% of cases of Down syndrome in the fetus.
- The result will be obtained in a long time. If the risk is high, you need to decide whether to do an amniocentesis (abstraction of amniotic fluid for research) to confirm or not.
The network describes various horrors after screening for Down syndrome ...
Decide if you are ready to accept the risky amniocentesis procedure if you are at risk for developing Down syndrome? And if the diagnosis is confirmed, will you decide to terminate the pregnancy at such a late date? In any case, before taking a screening test, you should seriously think about it.