First screening

The first screening is part of a set of diagnostic procedures during gestation. With the help of screening studies, a specialist can identify early deviations in the course of pregnancy, which will allow timely correction of possible violations. The results are interpreted by the doctor in conjunction with all screening methods.

Dates of the event

During the gestational period, a pregnant woman undergoes only three mandatory examinations. The time of the first examination is the first trimester. The exact date of natural conception is difficult to determine, the timing can vary within 3-5 days. Therefore, the obstetric calculation of pregnancy dates is based on the date of the last monthly period, the beginning of pregnancy is the first day of the last menstruation.

When prescribing the first screening during pregnancy, they are guided by obstetric terms, although edits in the date are possible if the menstrual cycle is long.

The minimum gestational period, when it is possible to detect signs of abnormal fetal development, as well as to assess the reaction of the mother's body to pregnancy, is 11 weeks. The deadline for the first screening is 14 weeks, or more precisely, 13 weeks plus 6 days from the start of the last menstrual period before pregnancy.

This period of screening during pregnancy is not accidental. At 12 weeks (obstetric), the embryo becomes a fetus, that is, it passes to another stage of development. If at this time the embryo has formed certain structures, then it acquires a new status in perinatal development (fetal or fetal). A pregnant woman should understand that it is important to observe the timing of screening during pregnancy, since the results of the diagnosis depend on it.

Who needs screening

Some women believe that if they feel well, it is not necessary to undergo screening during pregnancy, especially since not all pregnant women are registered with a gynecologist in the first trimester. Thus, women, especially those at risk, may give birth to a baby with physical or / and mental disabilities. After all, if you do not detect a chromosomal mutation in the early gestation period, the disease itself will not go anywhere, and embryogenesis will then go down the wrong path and there will come a time when it will not be possible to correct anything.

Therefore, regardless of the state of health of the pregnant woman, her age, the birth of previously healthy children, the presence of excellent living conditions and nutrition, screening during pregnancy is recommended to take place at all stages of gestation. Even with a woman's good health and unencumbered heredity, abnormalities in embryogenesis can still occur. Despite this, a pregnant woman can refuse to be examined, no one will force her to undergo a diagnosis.

Special attention should be paid to screening during pregnancy for women belonging to the risk group:

• expectant mothers 35 years of age and older, even if they have already given birth to healthy children. After this age period, the body begins to age, triggering processes in which the probability of chromosomal abnormalities in the fetus increases;
• the presence in the anamnesis or detection of signs of a frozen or ectopic pregnancy, miscarriage, risk of spontaneous miscarriage, premature birth;
• ARVI or other infection at the beginning of the gestational period;
• chronic infectious process, sluggish infectious diseases;
• stillborn children in the family or children with chromosomal abnormalities;
• close blood relatives of future parents who have been diagnosed with a genetic disorder;
• taking various medications, vaccination, anesthesia during surgery immediately before conception and at the beginning of gestation;
• conception as a result of incest or violent acts;
• tobacco smoking, alcohol abuse, drug use;
• rhesus conflict.

Screening during pregnancy does not pose any danger to the expectant mother and child, so it is unwise to refuse the examination.

What is included in the survey

The first screening includes two main diagnostic measures:

• Ultrasonography of the fetus and uterus of the future mother allows you to assess the course of fetal development, the correspondence of body parts to the gestational period, the development of age-appropriate structures. The health of the uterus and placenta is also evaluated
• Blood biochemistry makes it possible to determine the concentration of hormones necessary for healthy development and certain markers characteristic of this period.

The combined results of screening (ultrasound and blood tests) will allow the doctor to understand how correctly embryogenesis occurs, whether there are risks or signs of genetic abnormalities, what is the physical reaction of a woman to the development of another organism in her, a new life.

Preparation and implementation

To ensure that the results of the diagnosis are not affected by any factors and do not distort them, you need to prepare for screening during pregnancy.

The preparation stages include:

• avoiding foods that theoretically can cause allergies or have previously led to allergic reactions: all types of citrus fruits, strawberries, raspberries, exotic marine products, unseasonal fruits and vegetables, any products that have not previously been consumed. If you have an allergy shortly before the screening, you need to inform the leading doctor about it. Alcohol is excluded even in minimal dosages;
• before the tests, you can not smoke and drink water or other beverages;
• before the examination, you can take food for 8-12 hours;
• during 3-4 days before screening, you can not physically and psychoemotionally overload, do not do sports exercises, avoid stressful situations if possible (hormonal substances are extremely sensitive to the emotional background and physical activity);
• do not have sex for 2-3 days;
• try to empty your bowels;
• upon arrival at the clinic, you need to rest for 15 minutes, sit, calm down, otherwise the test results may be distorted.

At the first screening, the preparation for ultrasound examination depends on the examination method: transvaginal or transabdominal. In the first variant, the ultrasound sensor is inserted directly into the vagina, so before the manipulation, you need to release the bladder.

When examining the genitals and the fetus with an abdominal sensor (through the abdominal surface), it is necessary that the bladder is filled as much as possible. To do this, half an hour before the study, you need to drink 0.5-0.7 liters of liquid, better than plain water, do not visit the toilet for 4 hours before the ultrasound.

If during the procedure the fetus lies so that it is impossible to determine its parameters, then the patient is offered to walk a little, make torso bends, tighten the abdomen, and then relax, simulate a cough reflex.

Immediately after ultrasonography, venous blood is taken for biochemical examination. As part of a single screening, it is important to conduct both examinations without interruptions, since the blood formula during pregnancy is constantly changing and it is necessary to correlate the results of its study with the data of ultrasound diagnostics.

Fetal indicators

Screening during early pregnancy allows you to determine the characteristics of the fetus by comparing them with the norm.

Determine the following indicators:

• Coccygeal-parietal size (KTR) - for the first time, the "height" from the child's crown to the coccyx is measured. Since the baby is constantly in the fetal position (with the legs drawn to the chest), it is not possible to measure the exact growth. To assess the height, the corresponding length of the femur, humerus and forearm is taken.
• Head circumference (OG) – calculated from the diameter.
• The biparietal dimension (BPR) is the distance between the outer contours of the parietal bones and the inner contours, and the distance from the frontal bone to the occiput is also measured. The indicator is of particular importance for determining the method of delivery. If the baby's skull is large and the mother's pelvis is narrow, then a caesarean section is offered. This issue is resolved based on the results of screening for late pregnancy, but the first examination is necessary for comparative analysis with the second and third examinations.
• The thickness of the collar space (TVP) is the volume of fluid in the neck fold, which is characteristic only for the first trimester. With insufficient volume or the absence of a fold, it is possible to judge the risks of chromosomal mutations. The final conclusions are made in combination with other markers of embryogenesis.
• Nasal bone size - screening is informative if performed at 12-13 obstetric weeks. Bone pathology may indicate chromosomal abnormalities. In the course of scientific research, it was found that in children with Down syndrome, the nasal bone is pathological in more than 93% of cases.
• Features of the skull and brain.
• Heart rate (HR) – is determined for compliance with the age norm. If possible, the diagnostician examines the structures of the heart muscle, the location and size of the heart, large vessels.
• Parameters of the placenta – thickness, location of the chorion.
• The number of vessels of the umbilical cord.
• Assessment of amniotic fluid (volume, color).

In a pregnant woman, the ultrasound examines the throat of the neck, assesses the uterine tone. Sometimes you can even determine the sex of the child, but with this question it is better to wait until 20 weeks.

The main parameter of fetal viability at the first screening is considered to be heart contractions. The heart rate should not be lower than 100 beats / minute and higher than 200 beats / minute because this is an unfavorable factor in the prognostic plan. According to the localization and structures of the heart, as well as the location of the stomach, the presence or absence of gross deviations is judged. An experienced diagnostician by the location of these organs can detect signs of congenital heart defects.

Blood counts

Venous blood for biochemical analysis is taken from a pregnant woman on an empty stomach to determine the level of two important substances during pregnancy:

• Human chorionic gonadotropin (HCG) – begins to be produced by the chorion in the first days after conception. Before the 9-week period, the concentration of the hormone increases, the peak falls on the 11-13 week, then the production decreases
• Plasma protein-A (RARP-A) is a protein produced during gestation by fibroblasts of the outer shell of the placenta in large quantities.

Normal HCG values typical for the first trimester are 50000-55000 mME / ml.

Elevated HCG levels may indicate the presence of such conditions:

• history of diabetes mellitus or gestational diabetes mellitus;
• multiple pregnancy-a large concentration of the hormone is due to the fact that it is produced by several choriones;
• toxicosis of the first trimester;
• the fetus may have Down syndrome.

Low HCG occurs when:

• insufficiency of the placental complex;
• ectopic pregnancy;
• high risk of spontaneous interruption;
• the fetus may have Edwards syndrome.

Normal values of RARP-A typical for the first trimester (1-14 weeks) – 0.79-6.01 mEd/l. For screening during pregnancy, a low plasma protein A index is important, which may indicate:

• the immune response of the body of a pregnant woman;
• the threat of miscarriage;
• fetal death;
• insufficiency of placental function;
• the fetus has chromosomal mutations (Down or Edwards syndrome).

A high concentration of plasma protein A may indicate that the pregnancy is multiple, the fetus is too large, and the placenta localization is low.

For screening during pregnancy, highly sensitive tests are used to ensure that the test results are as accurate as possible.

Comprehensive decryption

Based on the results of screening during pregnancy, taking into account blood parameters and ultrasonography data, the following data will be reflected in the results:

• risk of developing a genetic abnormality;
• interpretation of a pregnant woman's blood test;
• the presence or likelihood of various pathological conditions;
• indicators of the IoM index.

The special program includes factors that can affect the health of the pregnant woman and the condition of the fetus: the age of the future mother, height, weight and their ratio, the number of fetuses, bad habits, the method of conception (natural or IVF), chronic diseases, and other data. To do this, the patient fills out a detailed questionnaire before the diagnosis. In the program with this information, the IoM coefficient is introduced, which is 0.5-2.5 units for one fruit, and 3.5 units for 2 or more fruits.

The computer program calculates all possible risks for the fetus, giving them in the form of a ratio of 1:1000. With low risks, the index will be at least 1:380, with a high probability of chromosomal mutations-below 1:380. This indicator is estimated, but not final.

Distortion of the results is possible when:

• multiple pregnancies;
• improper preparation for a biochemical study;
• conducting ultrasound on low-quality equipment;
• ECO;
• diabetes mellitus;
• overweight mother.

According to the results of the first screening, a final diagnosis is not made, but the probability of a serious fetal disease is revealed. To confirm or establish a final diagnosis, additional diagnostics are prescribed, mainly these are invasive diagnostic procedures. Also, most likely, you will need to consult a geneticist and other narrow-profile specialists.

It happens that already in the first trimester, irreversible disorders are found that are incompatible with further normal fetal development or even with the life of the fetus. In such a situation, it is recommended to terminate the pregnancy, but the decision remains with the parents. This is why screening in the early gestational period is so important, otherwise a woman may carry an unviable child for several months.

Another need and advantage in early diagnosis is that a reliable pregnancy period is established, and the date of birth is calculated on this basis.

What to do in case of unsatisfactory results

Some women are afraid of the first screening during pregnancy, because they are afraid to hear the disappointing news and that in this case they will be forced to have an abortion. But, first, to terminate a pregnancy or not – everyone's business.

Secondly, in doubtful situations, you can take the tests again, there may have been errors in preparing for the tests, so the results were incorrect. Either the examination was carried out on poor equipment and the woman needs to undergo screening tests in another clinic.

For example, in state medical institutions, you can get a diagnosis even for free, but the quality of medical diagnostic equipment can be questionable, as well as the laboratory tests used. Therefore, before the examination, you should think about it and perhaps choose a good paid clinic, so that the results of the diagnosis and their interpretation are not in doubt.

Third, increased risks - this does not mean that the disease is absolutely present. Many negative health factors can be corrected. In this case, the doctor will select individual recommendations that the pregnant woman should follow. Sometimes the correction consists only in changing the lifestyle, nutrition, reducing physical and psychological stress. Altravita provides top-level diagnostic services for pregnancy, as well as consultations with experienced, highly qualified specialists.

obstetrician-gynecologist Okuntsova E. A.