Not everyone is familiar with a term such as prenatal screening. Nevertheless, people who work in the field of health know almost everything about him. Moreover, the term "screening" comes from the English word screening, which in translation means selection or sorting. In other words, this means the process of selecting or rejecting something.
Remarkably, the term screening is used in many areas of human activity. In economics, this word means identifying reliable partners. As for health care, it involves examining people in order to detect the symptoms of a disease in the early stages.
In particular, prenatal examination is a whole range of studies that every pregnant woman undergoes. They allow you to detect various kinds of defects in the development of the child. Based on all the information received, both the expectant mother and the doctor are aware of the course of the pregnancy. And if there are risks, take the necessary measures in a timely manner.
general information
Let us consider in more detail what exactly is prenatal screening. After all, such a survey is carried out not only among expectant mothers, but also everyone else, depending on age. Moreover, the word "prenatal", in turn, means prenatal. Such a complex of medical research includes not only the delivery and processing of laboratory tests, but also hardware examinations (ultrasound).
The importance of prenatal research is difficult to overestimate or underestimate, because it allows you to control the development of the child, who is still in the womb. Moreover, it is possible not only to detect the deviations themselves, but also to identify all the possible risks of pathologies. Only on the basis of the data obtained from the screening, the doctor subsequently makes responsible decisions. That is, whether an additional examination is needed.
Most expectant mothers fear that waiting for test results might inevitably provoke stress. It is worth noting that a woman has the right to refuse this kind of screening if there is no desire or confidence in such procedures.
But if you look at everything from the other side ... If the expectant mother during pregnancy risk assessment at 1 screening reveals any abnormality in the development of the fetus, she faces a difficult choice: continue to bear a child with a pathology and raise him or terminate the pregnancy.
The essence of screening
Screening is aimed at informing a woman about the nature of the course of pregnancy. And if the expectant mother receives unwanted information, she will have time to mentally prepare for the birth of a special child. If there are no deviations, then there is no cause for concern either.
However, there are specific indications for prenatal screening:
- Women over 35 years old.
- If close relatives have a genetic predisposition to any disease.
- Families where children with a genetic and chromosomal abnormality or congenital malformations have already been born.
- If a woman has previously had an abortion procedure.
- The mother had cases of two miscarriages in a row or more.
- Conception came from a close relative of one blood.
- Taking medications for the period of the first trimester (until the 13-14th week), which are prohibited for pregnant women.
- One of the partners was exposed to radiation shortly before conception.
This is a kind of risk group for prenatal examination. Only here it should be clearly understood that this does not include women who are threatened by something during the necessary examinations, as it might seem at first glance. Everything is different here, because these procedures, which are part of a comprehensive prenatal screening, are completely safe.
The risk group includes those women who, for whatever reason, have a high degree of risk of developing anomalies in the child. In this regard, the course of pregnancy deserves increased attention.
What else is the need for screening
It is unlikely that anyone wants to argue with the importance of screening, although there may be those who wish. That's just for this it is worthwhile to give a strong argument in favor of the need to undergo routine examinations. In particular, we are talking about identifying many serious pathologies, which may include:
1. Down syndrome - a similar chromosomal disorder can be detected in the I or II trimester.
2. Edwards syndrome - can be detected at the same stages of pregnancy as the disease mentioned above. This chromosomal change is considered a serious pathology, which is often incompatible with life or ends with oligophrenia.
3. Anencephaly - prenatal pregnancy screening will detect this pathology, but only for the period of the second trimester. In this case, the development of the brain and spinal cord is malfunctioning.
4. Cornelia de Lange syndrome - refers to the category of hereditary diseases. Its symptoms are mental retardation and multiple developmental abnormalities.
5. Smith-Lemley-Opitz Syndrome - is an autosomal recessive disease associated with metabolic disorders. The result may be easy - minor defects on the physical level and intellectual disruptions. At the same time, there may be a severe form, which is expressed in a deep degree of mental retardation and severe physical defects.
6. Non-molar triploidy - is a rare chromosomal abnormality that does not end in anything good and often leads to fetal death in early pregnancy or it all ends in stillbirth. But even if the child survives, there will be many violations in his body, as a result of which he will not be able to live long - only a few weeks.
7. Patau syndrome is another chromosomal pathology that cannot be hidden from prenatal screening. Otherwise, it is called trisomy 13 or trisomy D. The incidence of children with a similar anomaly is 1: 7000-10000. Often with such a deviation, miscarriages or stillbirths also occur. However, if the child is lucky to be born, then he lives for no more than a week, since the work of the brain, heart is disturbed, pronounced defects of the spine and other no less serious pathologies are present.
It is a prenatal examination that can identify the listed pathologies in the fetus. For the most part, if there is a dangerous risk, a decision is made to terminate the pregnancy according to medical indications.
Screening Indications
Probably, many women, having heard about the screening, begin to think about whether there are any indications and contraindications here. Most likely, the foreign origin of the word is affected. But an important point should be clarified - screening refers to a whole range of studies, and the most elementary ones (blood test, ultrasound). As for the timing of prenatal screening, it is usually done as soon as a pregnant woman is registered.
In other words, the very fact of a successful conception and bearing a child is already becoming an indication for screening. And since all the manipulations are completely safe, then there are simply no contraindications here. There is only one important point - a woman should undergo any kind of examination while being healthy.
If there is any disease, the screening results may be distorted. This applies not only to acute respiratory illness (colds), but also to viral infections, including tonsillitis.
Therefore, before undergoing a screening, a woman should visit her attending gynecologist, ENT doctor, and general practitioner. Sometimes it is worth visiting other narrow specialists. This will allow women to make sure that they are completely healthy and nothing can distort the results of screening studies.
Types of Prenatal Screening
There are three main types of screening we are considering, as well as three main periods of pregnancy (trimesters). For clarity, the table below is shown in the photo.
In this case, different tests are carried out:
- Molecular - is indicated in cases when there are people in the family of mother or father who have been diagnosed with one of the following diseases: cystic fibrosis, Duchenne myodystrophy, hemophilia A and B, including other similar pathologies. If the patient wishes, then a check for the presence of these diseases can be passed before the onset of pregnancy or during gestation. The material for the study is blood from a vein.
- Immunological (prenatal genetic screening) - venous blood is also required for this test. Its purpose is to determine the blood group, Rh factor, as well as TORCH infections: rubella, cytomegalovirus, chickenpox, toxoplasmosis, herpes. This study, experts recommend conducting two times during the entire period of pregnancy - I and III trimester.
- Cytogenetic - a geneticist is engaged in a similar study, which does not require any equipment. The examination is conducted in the manner of communication between the doctor and the patient, during which the specialist can find out if the woman or her husband has hereditary diseases. If any, this is an occasion for a more detailed study. This test should be carried out while planning a child or during the first trimester.
As you can see, these tests are more likely to complement the main screening, which includes two more studies: ultrasound and blood biochemistry. But, in addition to this, invasive procedures are performed: a chorionic biopsy and amniocentesis. Only they are appointed in extreme cases.
Ultrasound screening
During the entire period of pregnancy, ultrasound should be performed at least three times:
- from 10 to 14 weeks;
- from 20 to 24 weeks;
- from 32 to 34 weeks.
This applies to the most basic dates, but if necessary, the doctor can prescribe any other time for this study. Often this is done in order to clarify the diagnosis made earlier.
The advantage of this non-invasive prenatal screening is that it allows you to visually identify any abnormalities in the development of the child, including growth retardation, which is especially important. Each year, up to 3 children are found out of every thousand newborns who have a crude form of developmental pathology that is not amenable to surgical correction.
Biochemical research
During biochemical screening, hormones are analyzed, which allows even early detection of possible genetic abnormalities. The most dangerous pathologies of all others are Down, Patau and Edwards syndrome. During the first examination, you can easily find the characteristic signs of deviation of Down syndrome. Only this is achieved only in combination with the first screening with ultrasound.
And they are:
- Significant excess of hCG level.
- Thickened collar space.
- At 11 weeks, the absence of new bone tissue.
Over the course of the second trimester, this syndrome has been detected by other signs: a more reduced level of AFP against the background of a high concentration of hCG. Therefore, blood biochemistry is done at least twice: from 10 to 14 weeks and from 16 to 20 weeks.
Conducting I Screening
How and when is such an important examination carried out? According to the table above, the first prenatal screening is performed - at 1 trimester. That is, from the 11th week of pregnancy to 13. During a visit to the gynecologist, who will conduct further monitoring, a woman will undergo a mandatory examination:
- growth measurement;
- determination of weight (which will make it possible to judge the nature of weight gain);
- blood pressure measurement;
- compilation of a complete medical history with the inclusion of the presence of any chronic and previous disease.
- If necessary, consultation from a highly specialized specialist is required.
Ultrasound is mandatory, during which an assessment is made of the state of the chorion, ovaries and uterine tone. Subsequently, it is from the chorion that the placenta is formed. In addition, an ultrasound scan at this time may show a single pregnancy or multiple pregnancy, including the development of the spinal cord, brain and limbs of the fetus (or both children).
In addition, at the prenatal screening of the 1st trimester, you also need to pass two tests: urine and blood. The latest study will not only determine the group and Rh factor, but also other risks like HIV, hepatitis and syphilis.
Screening II
The time for II screening is at the end of the first half of the entire gestation period - from 15 to 20 weeks. In this survey, those risks that were only suspected during the first inspection are now either confirmed or disproved.
And if during the prenatal biochemical screening chromosomal abnormalities in the fetus are detected, the woman will be asked to terminate the pregnancy due to medical indications, since the chromosomal pathology is not yet curable. In this case, the future mother faces a very crucial moment. Preservation of pregnancy may result in the birth of a child who will subsequently be disabled or completely unviable.
However, if neural tube defects are found during the second screening, they can still be eliminated completely or minimized. As for the procedures, an abdominal ultrasound is performed and blood is taken for biochemical analysis.
Ultrasound will show what position the child took, his anatomical development. In addition, the necessary measurements will be performed:
- limb length;
- head volume;
- chest volume;
- the volume of the abdomen.
As during the first screening, this information will make it clear whether the fetus develops skeletal dysplasia or not. Other important parameters are also being studied: the development of the brain, the formation of skull bones. It is estimated in what condition the organs of the cardiovascular system (CCC) and the gastrointestinal tract (GIT) are. All this allows us to judge the presence of any pathology or its absence.
A biochemical blood test is also referred to as a “triple test” in another way. In the course of it, the amount of the main hormones produced in the female body only during pregnancy is estimated - this is hCG, AFP. Comparison of the data obtained with the standards allows us to judge the development of the process of bearing a child. And if there are any anomalies, then it will be immediately visible to a specialist.
Features of III screening
The third time, screening is carried out from 30 to 34 weeks of pregnancy. Its main task is to identify some risks:
- premature birth;
- the likelihood of complications during the birth of a child;
- identification of indications regarding cesarean section;
- detection of intrauterine defects;
- identification of pathologies in the development of the fetus.
According to the decoding of prenatal screening, the last two deviations appear only at a later stage of pregnancy. As for the necessary procedures, there are three:
- Ultrasound
- Dopplerometric study.
- Cardiotocography (CTG).
In the course of a conventional ultrasound examination, the state of the fetal organs is evaluated, amniotic fluid is studied, including the condition of the placenta, umbilical cord, cervix and its appendages. All this allows us to determine the presence of obstetric complications during childbirth and identify malformations in the fetus.
Dopplerometry is a type of ultrasound and its main task is to determine the performance of the baby's circulatory system, including the uterus and placenta. Using this examination, it is possible to detect malformations in the development of the heart, the maturity of the placenta, its performance, the likelihood of entwining the fetus with the umbilical cord. You can also determine whether enough oxygen is being delivered to the fetus or whether it is deficient.
Cardiotocography records the fetal heart rate (HR), its mobility. In addition, you can find out in what tone the uterus is located. With the help of this study, it is possible to detect deviations of the cardiovascular system, and to reveal the fact of oxygen starvation.
Prenatal Screening Results
Deciphering the results of all conducted and necessary studies should be done only by a doctor and no one else. And in order for them to be reliable, several factors should be taken into account:
- gestation period;
- how old is the expectant mother;
- the presence of obstetric and gynecological pathologies;
- whether the pregnant woman has a bad habit, and any;
- what kind of life a future mother leads.
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