Timing of screening 2nd trimester of pregnancy. At what gestational age is the second prenatal screening performed, as shown by ultrasound
Description
Material under study Serum
The study is performed for screening examination of pregnant women in order to assess the risk of fetal chromosomal abnormalities - trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), as well as neural tube defect (NTD). Quantification of research results is carried out using PRISCA software.
Attention! For this study, the results of ultrasound are required!
Biochemical screening of the second trimester of pregnancy "triple test" of the second trimester consists of the following studies:
- Human chorionic gonadotropin (hCG, beta-hCG, b-hCG, Human Chorionic gonadotropin, HCG), test No. 66;
- Alpha-fetoprotein (AFP, a-Fetoprotein), test No. 92;
- Free estriol (unconjugated estriol, unconjugated estriol), test No. 134.
Determination of the concentration of these markers is used for screening of pregnant women in the second trimester of pregnancy in order to assess the risk of chromosomal abnormalities and fetal neural tube defects. The study is carried out between 15 and 20 weeks of pregnancy. The optimal timing for 2nd trimester screening is between 16 and 18 weeks of pregnancy.
Conducting a comprehensive examination at a period of 11-14 weeks of pregnancy, including ultrasound and determination of maternal serum markers (free beta-subunit of hCG and PAPP-A), followed by a complex program calculation of the individual risk of having a child with a chromosomal pathology, is recommended for all pregnant women by order of the Ministry of Health RF dated November 01, 2012 No. 572n (“Procedure for the provision of medical care in the field of obstetrics and gynecology”). If 1st trimester screening is normal, 2nd trimester AFP alone can be used to rule out neural tube defects (see AFP Test #92), or a complete 2nd trimester PRISCA profile. A triple biochemical test with a complex software risk calculation in the 2nd trimester may be especially appropriate for borderline risk assessment results during 1st trimester screening, and also if for some reason the 1st trimester screening was not carried out on time.
PRISCA (developed by Typolog Software, distributed by Siemens) is an EU-certified (CE-certified) and registered for use in the Russian Federation program that supports risk calculation for screening examinations of the 1st and 2nd trimesters of pregnancy. The risk calculation is carried out using a combination of biochemical markers informative for the corresponding period and ultrasound indicators. 1st trimester ultrasound data performed at 11-13 weeks of gestation can be used to calculate risks in the PRISCA program during 2nd trimester biochemical screening. At the same time, the PRISCA program will carry out an integrated calculation of risks, taking into account the value of NT (thickness of the nuchal space of the fetus) relative to the median values of this indicator for the gestational age at the date of its measurement in the 1st trimester.
The accuracy of the indicated individual data, the qualifications of the ultrasound provider in performing prenatal screening ultrasound measurements, and the quality of laboratory tests are essential for correct calculations.
Training
It is preferable to take blood in the morning on an empty stomach, after 8-14 hours of a night fasting period (you can drink water), it is permissible in the afternoon 4 hours after a light meal.
On the eve of the study, it is necessary to exclude increased psycho-emotional and physical activity (sports training), alcohol intake, an hour before the study - smoking.
Screening of the first trimester is optimal at 11-13 weeks, the second trimester - at 16-18 weeks. 1st trimester ultrasound data can be used to calculate risk in 2nd trimester biochemical screening.
Indications for appointment
Screening examination of pregnant women in the second trimester of pregnancy to assess the risk of chromosomal pathologies and a defect in the neural tube of the fetus, especially appropriate in case of borderline results of the calculated risk of chromosomal pathology during screening of the 1st trimester, and also if the screening examination of the 1st trimester was not carried out on time.
To complete the study, you must fill out.
Interpretation of results
The interpretation of test results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. An accurate diagnosis is made by the doctor, using both the results of this examination¤ and the necessary information from other sources: history, results of other examinations, etc.
The results of the survey are issued in the form of a report form. It indicates the data used in the calculations, provides the results of the studies, adjusted values of MoM. In the conclusion, quantitative indicators of the risk degree for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and neural tube defect (NTD) are indicated, which reflect the frequency of occurrence of the corresponding types of pathology with similar examination results and individual data. For example, a risk ratio of 1:6250 means that the statistical probability of having a child with the corresponding pathology is one in 6250 pregnancies with similar individual data. The PRISCA program sets conditional thresholds for identifying a high-risk group - a frequency above 1/250 for trisomy 21 (Down syndrome), above 1/100 - for trisomy 18, AFP MoM above 2.5 - for a neural tube defect.
The results of calculating the risk of fetal chromosomal abnormalities based on screening biochemical studies and ultrasound indicators are only statistical probabilistic indicators that are not the basis for making a diagnosis, but may serve as an indication for the appointment of further special research methods. According to the current recommendations of the Ministry of Health of the Russian Federation, when a pregnant woman is found to have a high estimated risk for chromosomal abnormalities in the fetus (individual risk of 1/100 and above), the obstetrician-gynecologist sends her to a medical genetic consultation (center) for medical genetic counseling and establishing or confirmation of the diagnosis using invasive examination methods to establish the fetal karyotype.
The use of complex (ultrasound + biochemical) screening, according to a number of studies, makes it possible to detect Down's syndrome in the fetus of pregnancy in 85 - 90% of cases with 5% of false positive results. Comprehensive screening helps to identify not only the risk of a fetal chromosomal abnormality, but also the overall risk of pregnancy pathology.
Screening of the 2nd trimester of pregnancy is a set of measures aimed at identifying possible pathologies in the fetus. It consists of an ultrasound examination and the so-called "triple test" (biochemical screening of the 2nd trimester). You can go through it between 14 and 20 weeks, but the period of 16-18 weeks of pregnancy is considered the optimal period.
How is 2nd trimester screening done?
This is an additional study, but it does not have any special indications for its appointment. So do not be surprised if the doctor recommends screening for the 2nd trimester - ultrasound and biochemical analysis. You can refuse both ultrasound and analysis, which, by the way, in most cases is paid. But still, in modern conditions, women often try to go through the maximum complex of diagnostics.
First, an ultrasound is performed. It will give a general understanding of the state of the fetus, the formation of its main systems. Also, ultrasound helps to more accurately determine the period, which is very important when deciphering the screening of the 2nd trimester - the norms are set strictly for each period of pregnancy. After that, it is important not to hesitate to donate blood for the “triple test”. Blood is taken from a vein and on an empty stomach, preferably the next day or in the days following the ultrasound. Biochemical screening of the 2nd trimester is aimed at determining the level of three specific substances in the blood:
- Human chorionic gonadotropin - hCG, by which most women find out about the onset of pregnancy with the help of home express tests;
- Alpha-fetoprotein - AFP, a protein that is produced in the body of the fetus and is responsible for protecting it from a possible threat from the mother's immunity;
- Free (unconjugated, unbound) estriol is a steroid hormone, the main estrogen of pregnancy, necessary for normal metabolism in the mother-child system.
Screening transcript 2nd trimester
According to the blood test, quantitative indicators are derived for all three test substances. Conditional norms for each period of pregnancy are derived.
Screening norms for the 2nd trimester are as follows:
- 16 weeks - 10,000-58,000 mU / ml;
- 17-18 weeks - 8,000-57,000 mU / ml;
- 19 weeks - 7,000-49,000 mU / ml.
Chorionic gonadotropin is usually measured in special units - mU / ml, they are also mIu / ml. Some laboratories use the measurement in nanograms - ng / ml. 1 ng = 1 honey: 21.28.
- 12-14 weeks - 15-60 U / ml;
- 15-19 weeks - 15-95 U / ml;
- 20-24 weeks - 27-125 U / ml.
- 13-14 weeks - 5.7-15 nmol / l;
- 15-16 weeks - 5.4-21 nmol / l;
- 17-18 weeks - 6.6-25 nmol / l;
- 19-20 weeks - 7.5-28 nmol / l;
- 21-22 weeks - 12-41 nmol / l.
In addition to these data, the average MoM coefficient is displayed - the ratio of indicators. Normally, MoM fluctuates between 0.5-2.0.
Is 2nd trimester screening necessary?
The first thing to emphasize is that this study is not necessary. The test results are unreliable and do not make it possible to make a diagnosis - only assumptions can be made from these data. The fact is that biochemical screening of the 2nd trimester can only indicate a certain probability of the presence of pathologies in the fetus. So if according to the ultrasound everything is fine, then this is just an additional confirmation. If screening was done in the first trimester, and its results did not cause concern, then your doctor is unlikely to insist on re-diagnosis.
The decision on whether to undergo screening for the 2nd trimester or not is made by the woman at her discretion. They recommend it to everyone without exception, since pathology can appear for no apparent reason, out of nowhere. So many people go through this study in order to reassure themselves in advance, getting rid of one of the worries about the health of their unborn baby. Others, clearly realizing that they will not terminate the pregnancy under any pretext, deliberately refuse this diagnostic method. However, a lot of experiences are experienced by those women whose blood counts did not fit into the screening standards of the 2nd trimester.
What should I do if my 2nd trimester screening results are not normal?
The main thing is not to panic! Whatever the deviations from the norm, it still does not mean anything decisively. Moreover, there are cases when, contrary to frankly frightening indicators, completely healthy babies are born. Unfortunately, it also happens vice versa - with ideal analyzes, in the end, everything does not go so smoothly. That is, the data obtained may well be false-negative or false-positive - the truth of the test does not exceed 70%.
The doctor, based on your specific case, will try to reassure you by pointing out the presence of factors that influenced the results of the 2nd trimester screening. And there are a lot of them: a cold, mother’s diabetes, low or overweight, smoking, taking medications, pregnancy features (not pathologies), etc. So if ultrasound did not show anything suspicious during screening of the 2nd trimester, then biochemical data are not taken into account. . Although you may well be sent for a consultation with a geneticist, it is unlikely that you will be able to get a specific answer from him - only assumptions.
In case of serious suspicions, it is proposed to continue the diagnosis with more serious methods. Unfortunately, they also cannot give an accurate result, but at the same time they take a lot of time and are fraught with a number of pregnancy complications (up to a miscarriage). And in the end, after all this mental anguish, you can get another one - an offer to have an abortion in the fifth or even sixth month of pregnancy, relying on unreliable research results. In addition to the moral and psychological aspects, such an intervention also significantly affects the physiology, posing a threat to the health of a woman. 4.6 out of 5 (45 votes)
Any examination prescribed by a doctor causes anxiety in most patients. This is especially true during pregnancy, when the expectant mother is no longer responsible for one, but for two lives. Of particular concern is the 2nd trimester screening. What is II screening? Why is the procedure necessary? And how many indicators are studied? All this excites expectant mothers.
Why is this study needed, and what do they watch in the 2nd trimester?
How many mandatory prenatal screenings are considered normal? The Ministry of Health of the Russian Federation insists on conducting 3 standard screening studies for all pregnant women. They are mandatory for representatives of risk groups:
- the woman has reached the age of 35;
- consanguineous marriage;
- heredity (there are chromosomal pathologies in the family, a woman has children with genetic abnormalities);
- several self-abortions in an obstetric history;
- the threat of miscarriage;
- oncopathology of a pregnant woman, detected after 14 weeks of gestation;
- radiation exposure before conception or immediately after it of any of the partners;
- SARS in the period from 14 to 20 weeks;
- anomalies and diseases of the fetus, identified by the 1st screening.
If an oncological pathology is detected in a pregnant woman, she is referred for a consultation with a geneticist in order to resolve the issue of the need for additional biochemical research in the II trimester. Quite often, a repeated ultrasound scan in a perinatal center or a specialized clinic is sufficient.
Maternal and child organs evaluated during screening
What is included in the second screening? At this stage of the examination, both the main fetometric indicators and the functional state of the organs and systems of the fetus are looked at:
- fetal vertebral column and facial bones of the skull;
- condition of the genitourinary system;
- the structure of the myocardium;
- the level of development of the digestive organs;
- anatomy of brain structures;
- basic fetometric data (BPR, LZR, OB, OG, lengths of tubular bones).
With a certain position of the baby, the doctor can see the sexual characteristics of the child. In addition to the general assessment of the fetus, they also look at the state of the organs and systems of the mother's body, on which the life of the baby directly depends.
The doctor carefully examines:
- placenta (location and condition, that is, thickness, maturity and structure);
- amniotic fluid (their quantitative indicators);
- umbilical cord (number of vessels);
- uterus, its appendages and cervix.
According to the data of the II prenatal screening, the doctor makes reasonable conclusions about the presence / absence of anomalies in the development of the fetus, as well as violations of its condition, blood supply and a threat to the health and life of both the mother and her child.
Preparations for screening
How many stages in the 2nd survey? The plan of diagnostic measures for a pregnant woman at the second screening includes stage II, they are not complicated and do not take much time, but require little preparation. Stages of the 2nd screening:
- a blood test for hormone levels (biochemistry) - currently performed according to indications.
Preparatory measures are not needed for ultrasound diagnostics. When performing the second screening, preparation is carried out for the sake of a biochemical test. You can’t eat before the analysis - he surrenders on an empty stomach. At least 4 hours should pass after eating. 30-40 minutes before the study, you can drink some water without gas, in the future it is better to refrain from taking liquids.
A blood test as part of screening is done on an empty stomach so that the results are as informative as possible. Based on the data obtained, the doctor identifies the compliance of the development of the fetus with the standards, and also checks the threat of genetic abnormalities Screening time 2nd trimester
When is the best time to do the research? There is a strictly defined time range for this. The timing of the second screening during pregnancy is as follows:
- Biochemical screening in the 2nd trimester is done in the period of 16-20 weeks. This time is diagnostically significant, both for the effectiveness of the ultrasound diagnostic procedure, and for donating blood for biochemistry and determining the level of hormones. The optimal time is 18-19 weeks.
- The procedure for perinatal ultrasound screening of the 2nd trimester is best done a little later - after biochemistry - at 20-24 weeks.
At the same time, it is not at all necessary to do an ultrasound scan and donate blood for biochemistry on the same day. But it is not necessary to delay the analysis. If ultrasound can be repeated regardless of the gestation period, then biochemical analysis is informative in a strictly specified time range.
How are the examinations carried out?
Ultrasound in the II trimester follows the same rules as any other ultrasound examination during pregnancy. It has no absolute contraindications. The ultrasound procedure is painless, non-invasive and is considered one of the safest methods for examining a future mother and her baby. During the examination, the woman lies on her back in a comfortable position, the doctor lubricates the skin at the point of contact of the sensor with the skin with a hypoallergenic gel and performs diagnostics. The study is carried out through the anterior abdominal wall. The woman receives the results and interpretation of the data in her hands within a few minutes.
Blood for biochemistry is taken on an empty stomach. For the study, a small amount of venous blood is taken. Before the start of the study, it is necessary to provide personal data and data from ultrasound diagnostics. The obtained data is analyzed using special software. Results are ready within 14 days.
Results of biochemical screening
Data decryption is carried out by qualified personnel. He evaluates a number of indicators, each of which is compared with the norm. When deciphering a blood test, the level of the following hormones in the blood is assessed:
- AFP (α-fetoprotein);
- E3 (estriol);
- HCG (human chorionic gonadotropin).
The norm of indicators of the second screening study directly depends on the period of pregnancy. For the II trimester, the norms are given in the table:
| Deadline (weeks) | EZ (nmol/l) | hCG (mU / ml) | AFP (u/ml) |
| 16 | 5,4-21 | 10-58 | 15-95 |
| 17 | 6,6-25 | 8-57 | 15-95 |
| 18 | 6,6-25 | 8-57 | 15-95 |
| 19 | 7,5-28 | 7-49 | 15-95 |
| 20 | 7,5-28 | 1,6-49 | 27-125 |
In some cases, the level of an inhibitor of FSH secretion (inhibin) is also evaluated. The evaluation of indicators of the II-nd screening is based on the average value (MoM). The average value is calculated using a special formula, taking into account the following data:
- body weight of a pregnant woman;
- age indicators;
- place of residence.
Average norms of hormone levels should be in the following range: from 0.5 MoM to 2.5 MoM. If the results are not within the specified range, the woman is referred for re-consultation by a geneticist. Biochemical data show the degree of risk of fetal diseases with genetic diseases, such as:
- Down syndrome;
- Patau syndrome;
- Edwards syndrome and others.
The norm is considered to be an indicator exceeding the risk of 1:380. A high degree of risk (1:250-1:360) requires a mandatory consultation with a geneticist. At extremely high degrees of risk (1:100), additional diagnostic measures are required. These are invasive measures, they carry a certain amount of danger to the mother and fetus, but they allow you to confirm the presence and type of anomaly by examining the baby's chromosome set.
HCG (chorionic gonadotropin) is the main “pregnancy hormone” that appears in a woman’s body. It is he who is a key component of determining pregnancy using a test. In the process of development of the future baby, the amount of the hCG hormone is constantly increasing, it has its own norms at each gestation period Results of ultrasound diagnostics
Ultrasound of the second screening is a complex study. It allows you to assess the condition of the reproductive organs of a woman, the fetus and the structures that ensure its life and development. During an ultrasound examination, the doctor evaluates:
- facial bones of the skull, facial features, their size and location;
- development of the eyeballs;
- spinal column;
- the state of the lungs, the degree of their maturity;
- development of brain structures and heart;
- genitourinary and gastrointestinal systems;
- indicators of fetometry of the fetus;
- the presence of visually distinguishable genetic anomalies (number of limbs, fingers).
Thanks to ultrasound of the 2nd screening, the doctor has the opportunity, based on sufficiently reliable data, to judge the degree of development of the fetus, the gestational period, the presence / absence of defects in internal organs, its viability.
Standards for screening indicators by week
The norms for some periods of gestation are shown in the table below. A period of 20 weeks is the last period when it is possible to determine and compare the levels of hormones in the blood. If for some reason a woman was not able to donate blood for biochemistry during this period, in the future this analysis loses its information content. Therefore, only the Doppler and CTG procedure is performed.
If a woman has not passed a biochemical blood test for up to 20 weeks of pregnancy, it is no longer relevant. To determine the condition of the fetus, dopplerometry is prescribed, which clearly demonstrates the supply of organs and systems of the baby with blood, and also allows you to see the blood flow in the uterus, placenta and umbilical cord For a period of about 22 weeks, only ultrasound is performed, blood sampling for biochemistry is no longer performed. This is the final time period for making a decision about medical termination of pregnancy. Medical abortion is done up to 22 weeks, after 23 - termination of pregnancy is carried out by the method of artificial childbirth.
| Indicator | 16 weeks | 20 weeks | 22 weeks |
| OG | 112-136 mm | 154-186 mm | 178-212 mm |
| DP | 15-21 mm | 26-34mm | 31-39mm |
| DPP | 12-18 mm | 22-29 mm | 26-34mm |
| DB | 17-23mm | 29-37 mm | 35-43mm |
| coolant | 88-116 mm | 124-164 mm | 148-190 mm |
| DG | 15-21 mm | 26-34mm | 31-39mm |
| LZR | 41-49 mm | 56-68 mm | |
| BDP | 31-37mm | 43-53 mm | 48-60 mm |
| IAH | 73-201 mm | 85-230 mm | 89-235 mm |
| Maturity of the placenta | 0 | ||
| Placenta thickness | 16.7-28.6mm |
The table contains the following data:
- OG - head circumference,
- DP - length of the humerus,
- DPP - the length of the bones of the forearm,
- DB - length of the femur,
- OC - abdominal circumference,
- DG - the length of the bones of the lower leg,
- fronto-occipital and biparietal dimensions,
- amniotic fluid index (AFI).
These are the main indicators that are informative regarding the development of the fetus, the presence or absence of structural abnormalities in it.
What can affect screening results?
If the data obtained during the examination correspond to the standards, the probability of having a healthy baby is very high. However, the percentage of error in this diagnosis still exists. And even not very good examination results do not always indicate a possible pathology.
That is, with poor performance, there is a chance that the baby will be born healthy, but even in a baby who was considered healthy throughout the entire gestation period, this or that pathology may be revealed after childbirth.
There are also a number of factors that affect the results of the examination, especially the biochemical test. These include:
- maternal chronic illness (eg, diabetes);
- bad habits (alcoholism, smoking, drug addiction);
- the weight of a pregnant woman (with excess weight, the indicators exceed the norm, with insufficient weight, they are underestimated);
- multiple pregnancy;
- pregnancy through IVF.
If a fetal pathology is detected that will lead to non-viability, severe deformities or developmental pathology, the woman is recommended to undergo additional, invasive examination methods (amniocentesis, cordocentesis), as well as an additional ultrasound procedure. In any case, the decision to maintain or terminate the pregnancy is made by the woman herself. The doctor can only give recommendations. Even if the pathology is confirmed by all studies with a high degree of certainty, a woman has the right to keep the pregnancy.
The examination in question is carried out between 16 and 20 weeks of pregnancy, and it consists of two stages: ultrasound and biochemical screening. In the absence of any abnormalities on ultrasound, a triple test is often not prescribed.
In general, screening of the second trimester of pregnancy is a voluntary procedure. In some cases, the results may turn out to be false positive, which provokes stress and negatively affects the health of the mother.
On the other hand, thanks to such a diagnosis, it is possible to identify and timely eliminate factors that interfere with the normal course of pregnancy.
Ultrasound procedure
This type of diagnosis makes it possible to make a complete assessment of the level of fetal development, confirm or refute the presence of physiological abnormalities.
Due to the age of the baby, using an ultrasound sensor, you can record the following indicators:
1. Gender
Gender can be determined if the embryo is positioned appropriately.
Otherwise, future parents will remain in the dark until the next screening, or until the birth of a child.
2. Fetometric data of the fetus
Includes several components:
- The length of the humerus and bones of the forearm . The doctor checks the presence of all bone tissue, the symmetry of the forearms.
- Dimensions of the femur and lower leg bones. The number of fingers and toes is taken into account
- Abdominal circumference.
- Fronto-occipital size and biparental parameters of the head of the embryo.
- Head circumference .
- The length of the nasal bone. The norms of the object of study under consideration are: 3.7-7.3 mm at 16-17 weeks of pregnancy; 5.3-8.1 mm at 18-19 weeks; 5.8-8.3 mm at 20-21 weeks. If the previous indicators are normal, but there are deviations from this component, it is considered that the fetus does not have any chromosomal abnormalities.
With significant deviations from the norm of all these indicators, there are two options:
- The age of the fetus was initially determined incorrectly.
- The embryo develops with certain pathologies.
3. Anatomical information
The doctor fixes the following nuances:
- The presence of kidneys, their symmetry.
- Location of internal organs: bladder, lungs, stomach, etc.
- The structure of the facial bones. On this ultrasound, defects in the anatomy of the upper lip can be detected.
- The structure of the heart in a four-chamber section.
- Dimensions of the cerebellum, lateral ventricles of the brain, large cisterna of the embryo.
4. Information about the placenta
The most successful place for attaching the placenta is the posterior wall of the uterus, or the area close to its bottom.
In that situation, if the placenta is located on the anterior wall of the uterus, there is a risk that its detachment will occur in the future.
The structure of the placenta from 16 to 20 weeks should be homogeneous. In the presence of deviations, treatment is prescribed aimed at normalizing blood circulation.
5. Amount of amniotic fluid (amniotic fluid)
With a slight oligohydramnios, therapeutic measures are limited to vitamin therapy, correction of the diet, and limitation of physical activity.
Severe oligohydramnios requires more serious measures, which will include the use of special medications. This is due to the fact that such a phenomenon can adversely affect the development of the limbs and spine of the embryo, provoke anomalies in the nervous system. Often, children who were born in conditions of oligohydramnios suffer from mental retardation and thinness.
No less dangerous for the fetus is pronounced polyhydramnios. A pregnant woman in such situations is most often hospitalized and complex treatment is prescribed.
6. Number of vessels in the umbilical cord
The condition is considered normal when the fetus has two arteries and one vein.
In those situations when the ultrasonographer revealed fewer vessels, you should not panic. Good results of the biochemical blood test, as well as the absence of abnormalities in the development of the fetus (according to ultrasound diagnostics) indicate that the only artery fully compensated for the work of the missing one.
If on the umbilical cord the child is diagnosed with the presence of only one vessel, most likely he will be born with a small weight, and as he grows, errors in the work of the heart may occur. This situation requires regular monitoring by the appropriate doctor.
In the future, parents should monitor proper nutrition, strengthen the protective reactions of the baby's body.
7. Parameters of the cervix and walls of the uterus
The doctor pays attention to the size of the cervix.
If, compared with the previous screening, there is a shortening (less than 30 mm), opening or softening of its tissues, a pessary may be prescribed to maintain the pregnancy.
triple test
After undergoing an ultrasound examination, the next stage of screening awaits the pregnant woman: a biochemical analysis of venous blood.
The main task of this testing is definition of three indicators:
1. Free estriol - sex hormone, which makes itself felt from the first days of placenta formation, and the level of which increases every month: 1.18-5.52 ng / ml at 16-17 weeks of pregnancy; 2.42-11.20 ng/ml at 18-19 weeks; 3.9-10.0 at 20-21 weeks.
A critical (40% or more) decrease in the hormone in question may be the result of several phenomena:
- There is a risk of miscarriage.
- There are certain anomalies in the development of the neural tube of the embryo or its internal organs. In particular, this applies to the adrenal glands.
- Serious disturbances occurred in the structure of the placenta.
- There is an intrauterine infection.
- The fetus is diagnosed with Down syndrome.
- At the time of the triple test, the pregnant woman was treated with antibiotics.
The level of free estriol in the blood of a future mother can increase in several situations:
- Pregnancy is multiple.
- The weight of the embryo exceeds the allowable rate.
2. Free beta hCG. It is this indicator that favors the appearance of a second strip when passing a pregnancy test.
The level of human chorionic gonadotropin in the second trimester of pregnancy can vary: 10-57 thousand ng / ml at the 16th week; 8-57 thousand ng / ml at 17-18 weeks; 7-48 thousand ng / ml at the 19th week of pregnancy.
The amount of free beta-hCG in the blood may increase if:
- The embryo develops with Down syndrome (with a deviation from the norm by 2 times).
- A woman is carrying more than one child.
- There are pathologies associated with increased blood pressure, swelling. A general urine test in this case states the presence of protein.
- A pregnant woman is diagnosed with diabetes.
- The fetus develops with certain defects.
- There are pathologies in the structure of the fetal egg. In 40% of cases, this phenomenon can provoke the appearance of choriocarcinoma.
A low level of hCG may indicate the following phenomena:
- There is a risk of miscarriage.
- The embryo does not develop correctly or does not develop at all.
- Embryo death has occurred.
- The placenta is not able to fully perform its functions due to violations in its structure.
- The fetus has either Edward's syndrome or Patau's syndrome.
With an incorrectly defined period, the level of hCG will also not meet the standards.
3. Alpha-fetoprotein (AFP). The specified protein is produced in the liver or in the gastrointestinal tract of the embryo, starting from the 5th week of pregnancy.
Amniotic fluid promotes the release of AFP into the mother's circulatory system, and from the 10th week of pregnancy, the level of this protein gradually increases.
At 15-19 weeks of pregnancy, the allowable rate of alpha-fetoprotein varies between 15-95 U / ml, after the 20th week - 28-125 U / ml.
An increase in the amount of AFP in the blood of a pregnant woman can be the cause of the following phenomena:
- There are errors in the structure of the neural tube of the fetus.
- The intestines or duodenum of the embryo have malformations.
- The baby has Meckel syndrome (in extremely rare cases).
- Necrosis of the liver, which was the result of infection of the body of a pregnant woman.
- There are anomalies in the structure of the anterior abdominal wall.
If the ultrasound confirms multiple pregnancy, doctors rarely prescribe biochemical screening: existing norms are applicable to singleton pregnancies.
It is very problematic to determine exactly how the indicators will change if a woman bears two or more fetuses.
Bad second screening - what to do and where to go next?
With positive results, expectant mothers should not immediately panic - in 10% of cases, such results turn out to be false.
However, if the risk ratio is 1:250 according to the screening program, the pregnant woman should turn to genetics. This specialist may prescribe additional non-invasive diagnostic methods, through which the presence / absence of chromosomal or congenital abnormalities in the fetus is determined.
If the risk is estimated as 1:100, it is recommended to undergo invasive research methods, or to undergo a non-invasive prenatal test:
- . It involves testing the amniotic fluid, for which the doctor pierces the peritoneum to collect it. The effectiveness of such an analysis is 99%, but such a procedure can cause a miscarriage in the near future.
- Cordocentesis. The test material is the umbilical cord blood of the embryo. To collect it, the doctor inserts a needle into the uterus by puncturing the anterior peritoneum. This procedure is advisable to carry out in the intervals between 22 and 25 weeks, but not earlier than 18 weeks of pregnancy. The manipulation under consideration in rare cases can cause intrauterine infection or miscarriage.
- Non-invasive prenatal test (NIPT). Can be prescribed as early as the 10th week of pregnancy. Mother's venous blood is used to test the fetal DNA. An embryonic DNA sample taken by sequencing is checked for a variety of chromosomal abnormalities. A negative result is almost a 100% guarantee of the absence of anomalies in development. With positive results, the passage of the invasive diagnostic methods described above is required. .
If the invasive diagnosis confirms the unfavorable results of the second screening, the woman has two options:
- Terminate pregnancy. The longer the period, the more serious the consequences for the health and psyche of the woman. However, with competent rehabilitation measures, parents will soon be able to start planning the next pregnancy.
- Leave the child. When making such a decision, future parents should be aware of all the difficulties that they will face in raising a seriously ill baby.
Hello dear readers! Today we will talk about what, on the one hand, makes us, future mothers, literally experience butterflies in our stomachs in anticipation of the next meeting with the baby, and on the other hand, not to find a place for ourselves from unrest. And once again brush aside the thought: “What if something is wrong with him?”
Guess what I'm talking about? Of course, about the new comprehensive examination, which now falls on the second trimester. And his name is the second screening during pregnancy. The timing of its implementation, standard indicators and deviations from the norm are the main issues that interest most women. We will talk about them.
The second screening, or screening of the 2nd trimester, is a diagnostic study, the purpose of which is also to identify the risks of developing pathologies in the fetus.
Traditionally, it includes an extended ultrasound and a biochemical blood test. Interestingly, the latter is called triple in terms of the number of proteins and hormones studied.
What does it include? Level test:
- free estriol;
- alpha-fetoprotein.
All of them allow assessing the condition of the fetus and identifying pathologies of the liver, intestines, kidneys, adrenal insufficiency, neural tube and spinal canal defects, ichthyosis and Smith-Lemli-Opitz syndrome, as well as detect preeclampsia and diabetes in the mother herself.
2. When and to whom is the second screening done?
What is the duration of it? It is difficult to answer unambiguously. The fact is that some experts advise to undergo a second screening at 16-20 weeks, focusing on the fact that the results of the same biochemical test, or blood test, are considered as accurate as possible if the material for research was taken strictly from 16 weeks to 6 weeks. Day 18 of the week. Others insist that you can wait until 22 - 24 weeks.
So, when is the second screening actually done? Quite a logical question, which can only be answered by a doctor observing pregnancy. Simply because he alone sees the results of the previous screening, on the basis of which he decides when it is better to do screening in each individual case. Or generally advises to refuse it. After all, such a study is not a mandatory procedure and is shown only to women who are at risk. Guess who it is?
- women over 35;
- those who had or have a threat of interruption or even worse complications in previous pregnancies, miscarriages;
- those who suffered acute bacterial or infectious diseases in the early stages and, as a result, took drugs that are contraindicated during pregnancy;
- those who have children with genetic diseases or family members with congenital malformations;
- those who had neoplasms in the 2nd trimester;
- those whose previous screening revealed a high risk of developing malformations.
Along with them, a future woman in labor will most likely be invited to the second screening if the father of her child is her blood relative. Everyone else will be given only a referral for a second ultrasound to assess the general condition of the fetus, which is usually carried out at 22-24 weeks of pregnancy. Although if they also want to undergo another screening and once again make sure that there are no risks, they are unlikely to be refused.
3. How to prepare for the second screening
The good news at this time for the expectant mother will be the absence of the need for thorough preparation for an extended ultrasound.
And this means that it is no longer necessary to drink liters of water immediately before the procedure, filling the bladder and holding back, but thus providing the specialist with a kind of viewing window. Now this function is performed by amniotic fluid.
Unfortunately, this news does not apply to the biochemical test. There, as before, a special diet is important, thanks to which you can get the most accurate results.
What should be excluded? That's right, allergens and junk food, namely:
- cocoa;
- chocolate;
- citrus;
- seafood;
- excessively oily;
- roast.
But the main thing here is not to get upset. You need to suffer only a day on the eve of the biochemical test. On the day of its direct conduction, it is necessary to come to the laboratory on an empty stomach. How is the test done? Like a normal blood test from a vein.
4. Normative indicators at the second screening
What do you think this study shows? That's right, the approximate weight of the fetus and the dynamics of its development.
Based on the results obtained, the specialist can judge:
- the structure of the fetus (does it have arms, legs, fingers, spine, etc.);
- the state of internal organs (brain, heart, kidneys, stomach, liver, etc.);
- fetal parameters;
- condition of the placenta and cervix;
- quantity and quality of amniotic fluid;
- the field of the future baby.
Upon completion, he issues a conclusion with the data obtained. Comparing them with the norms, we can talk about the health of the unborn baby. For your convenience, we have arranged them in the form of a table: