A expectant mother throughout the entire period of bearing a baby will have to undergo a number of different diagnostic studies in order to monitor the health of the woman and her fetus. Some tests are mandatory, while others are advisory in nature. Such is biochemical screening. What is it, why is it carried out and what pathologies can be detected with its help, we will consider in the article.
What is biochemical screening during pregnancy?
This method of diagnostic research has become widespread in medical practice recently. Initially, it was carried out exclusively according to the doctor’s testimony with the aim of early diagnosis of certain genetic pathologies. But due to accessibility and effectiveness, this method was also used in preventive research. Now a pregnant woman without special medical indications can optionally undergo such a test.
So, biochemical screening - what is it? This is a venous blood test to determine chromosomal pathologies. But the screening results cannot be the final diagnosis, with one hundred percent accuracy using this method it is impossible to confirm the presence of a chromosomal disease. Only the probability of such a pathology in each specific case is determined.
In order to correctly interpret the obtained results of biological analysis, immediately before blood sampling, a pregnant woman is sent for ultrasound examination. So, at the ultrasound the doctor takes measurements of the fetus, evaluates its condition. Deviations from the established norms together with high rates of the results of a biochemical blood test can indicate the presence of a genetic pathology in the fetus. If a high probability of a fetus having a chromosomal disease is detected, specialists may recommend additional diagnostic procedures. For example, in this case, doctors can prescribe an intrauterine examination of the material in order to make a final diagnosis.
Thus, only the probability of the presence of a chromosomal pathology is determined by biochemical screening. What kind of analysis is this, how it is carried out, we will find out later in the article.
Screening Indications
As indicated above, the study is conducted both for prophylactic and for clinical purposes. Mandatory screening is in such cases:
- if the couple is close relatives;
- a pregnant woman had any infection shortly before pregnancy and immediately during the indicated period;
- a history of missed pregnancy, stillbirth, miscarriage, premature birth or the birth of children with genetic defects;
- the family has relatives with chromosomal diseases;
- future mother's age exceeds 35 years;
- the pregnant woman took medications that were prohibited during the period of bearing the child, or was exposed to x-ray, as well as radiation;
- shortly before conception, the future father or mother underwent radiation therapy or x-ray examination;
- the results of an ultrasound examination of a pregnant woman are doubtful, and it is recommended to conduct a perinatal biochemical screening (this and whether it is dangerous for a pregnant woman to do this, the attending physician will tell in detail).
What determines the analysis?
Biochemical screening is carried out two or three times throughout pregnancy. And depending on the period with its help, various chromosomal abnormalities in the fetus are diagnosed:
- Edwards syndrome;
- Patau syndrome;
- Down syndrome;
- Lange syndrome;
- the presence of a neural tube defect.
The first three diseases have such a common name as trisomy. Biochemical screening helps doctors identify such anomalies in chromosome junctions in the early stages. What are these pathologies, what are dangerous? In the presence of trisomy during a biochemical blood test of a pregnant laboratory assistants detect 22 pairs of normal chromosomes and one "triple". Depending on where exactly the pathology was formed, and diseases are distinguished.
First trimester screening
In medical practice, they often resort to such an analysis as biochemical screening of the first trimester. What is it, what is it for and when is it done? For the first time, a pregnant woman is faced with the concept of screening for a period of 11-14 weeks. Such an examination includes an ultrasound, in which the doctor measures the collar space of the fetus, and clarifies the gestational age and PDE.
After an ultrasound examination, the woman is sent by a doctor for a blood test. At this stage, human chorionic gonadotropin and PAPP protein are determined. Based on the results obtained, specialists may suspect abnormalities in the development of the fetus, including the detection of a chromosomal pathology such as Down syndrome.
Also called a "double test" biochemical screening of 1 trimester. What it is? The study at the 11-14th week of pregnancy acquired this name due to the fact that a blood test is carried out for two specific substances: hCG and protein PAPP.
First Trimester Screening Standards
HCG and PAPP indicators are influenced by external factors, such as the weight of the pregnant woman, location and climate of the territory of residence, gestational age and others. In order to adapt the standards for most women, such units of measure as MoM have been developed. Norms of biochemical screening are calculated precisely in such units. In order to calculate them, the results of a pregnant woman’s blood test are divided into normal values ​​established for a particular area, period and weight category of women. Thus, if the result is 0.5-2.5 MoM, then the hormone is within normal limits. But above 2.5 MoM indicates a high risk of chromosomal pathologies.
Second trimester screening
A biochemical screening of 2 trimesters has been prescribed: what is it and why is it necessary to undergo such an examination? A second screening may be scheduled for 16–18 weeks. During such a comprehensive examination, ultrasound diagnostics will be carried out, if necessary in 3D format, during which the doctor will measure the fetus, evaluate its heart rate and position in the uterus.
A blood test will be performed to determine three or five hormones, such as: hCG, PAPP, estriol, placental lactogen and inhibin. Such an analysis is also called a triple test.
If necessary, the expectant mother can be sent for a consultation with a geneticist who will evaluate the results of the second trimester screening and give recommendations.
Third trimester screening
Screening in the third trimester is most often performed according to the doctor’s testimony at weeks 32–34. During an ultrasound examination during this period, the doctor assesses the state of development of the internal organs of the child, its presentation, the presence or absence of cord entanglement, the state of amniotic waters and the placenta. Blood is tested in a triple test.
The features of the third trimester screening are additional diagnostic tests in the form of Doppler and CT. Using the first procedure, blood flow is assessed and fetal hypoxia is determined. And the second defines disturbances in the work of the heart. These procedures are carried out in the same way as ultrasound, being absolutely safe and painless for a pregnant woman and her child.
Screening Preparation
Did the doctor recommend a biochemical screening? How to take an analysis to get the right results? Proper preparation for screening is an important component that determines the reliability of the results. So, for example, if nutrition recommendations are not followed during chemical reactions, laboratory assistants will receive only a fat mass, from which it will be difficult to determine anything. Therefore, one day before perinatal screening at any stage of pregnancy, you can not eat these products:
- spicy food;
- smoked meats;
- fatty and fried;
- chocolate;
- strong black tea and coffee;
- citruses.
Fasting blood is given.
Analysis
Screening usually takes place in two stages. The first involves an ultrasound examination. Only after receiving the results of ultrasound, you can go for a blood test. Typically, the results of biochemical screening can be obtained only after a fairly long time - from one and a half to three weeks. In private clinics, analysis is possible in an accelerated time - up to a week.
Is screening required for pregnant women? Screening is a recommended test for a pregnant woman. On the one hand, thanks to such a simple and safe study, you can find serious pathologies of the development of the baby in the early stages. But at the same time, diseases defined in this way are not treatable. In addition, the results only indicate the degree of risk of developing disorders and are not a diagnosis. If abnormalities are found, the expectant mother becomes a difficult choice for the further development of pregnancy. Therefore, the final decision regarding the passage of such an examination can only be made directly by future parents.
Decryption
Deciphering biochemical screening requires professional knowledge. Only the attending physician can interpret the results. It is important to take into account and compare various factors, compare norms, and assess predisposition to genetic diseases.
The blood test is decrypted as follows:
- 1:10 000 is a low risk of developing pathologies;
- 1: 1000 - average;
- 1: 380 - high, requiring additional research.
Ratios indicate how many pregnancies a case of pathology is possible. That is, for example, at low risk, the probability of developing a chromosomal disorder is 1 in 10,000.
Patient Reviews
Pregnant women are looking forward to seeing their baby on an ultrasound scan. But at the same time, such an examination brings a lot of emotions. Often, external factors influence the screening indices, and deviations do not find confirmation when conducting a second study. But during this time, the expectant mother experiences serious fears associated with the unknown and the identified danger, which is extremely negatively reflected in her condition and the development of crumbs.
That is why patient reviews about the innovative diagnostic method are mixed. Some with confidence go to the examination with the aim of early detection of impaired development of the child, while others refuse moral and spiritual views.
Screening Cost
Another factor that contributes to the rejection of expectant mothers from perinatal screening is its cost. Only in the case of referral according to indications and conducting an examination in the conditions of a state clinic or a hospital, analysis can be an insurance case.
If screening is carried out at will for preventive purposes or in a private clinic, you will have to pay from 5,000 to 9,000 rubles, depending on the clinic and the equipment used in it.
In our article, we examined why it is important to undergo biochemical screening, what it is, how it is carried out, and what indications it has. The decision about whether or not to undergo such a study should be taken by the pregnant woman together with the doctor. And importantly, tune in to a positive result and a reasonable assessment of the received analysis responses.