1st screening results. Biochemical screening. Norm. Decoding the results. What types of birth defects are screened for?

1st trimester screening is included in the general set of examinations during the gestation period to assess the child’s health and possible threats to pregnancy. Screenings are a common research method that applies not only to pregnant women: referrals for screening studies are also prescribed for newborns, as well as any population groups included in the risk group for developing any diseases, abnormalities, or dysfunctions.

Screening studies allow you to determine the likely possibility of pathology. In the first trimester of pregnancy, screening combines ultrasound examination and analysis of blood parameters, while interpretation of the results is carried out exclusively in a comprehensive analysis of both types of research.

First screening during pregnancy: period and timing of the study

During pregnancy, women are asked to undergo three screenings to identify and promptly correct possible deviations in the course of pregnancy or fetal development.

1 screening is carried out in the first trimester. The timing of pregnancy in the classic version is established on the basis of obstetric calculation, where the first day of the gestational period is considered the date of the beginning of the last menstruation before the onset of pregnancy. With the calendar method of determining the duration of pregnancy, experts start from the day of conception. However, since during physiological conception it is difficult to determine this date (the day of ovulation and the day of fusion of the egg and sperm may differ by 3-5 days), it is recommended to adhere to the obstetric technique, focused on the date of the last menstruation.

With a long menstrual cycle, the specialist can make changes to the screening dates, however, on average, the first screening test is carried out between 11 and 14 weeks of gestation, limiting the upper limit of the period to 13 weeks and 6 days from the date of the start of the last menstrual bleeding.

Why was this particular period chosen for the first screening? At 12 obstetric weeks, the border between the embryonic and fetal or fetal periods of development passes: the unborn baby passes from the embryonic stage to the fetus. The presence of formed structures and changes in the body make it possible to assign a new status to the future baby at the perinatal stage of development.

Also, this period is the minimum during which it is possible to identify the most common, although quite rare, deviations, as well as the reactions of the mother’s body to the development of a new life.

Screening – voluntary or obligatory?

Since early diagnosis of possible abnormalities allows you to quickly and effectively help the expectant mother correct possible negative consequences, screening studies during gestation are strongly recommended for all pregnant women, regardless of age, health status and the presence of healthy children. Deviations recorded during the study can occur spontaneously without correlation with the health of parents, relatives and lifestyle.

Despite the fact that the screening study is carried out on the direction of a gynecologist, you can refuse screening. This procedure is voluntary, although it is recommended by the Ministry of Health as part of the medical support of pregnancy for any woman.

If you refuse screening for one reason or another, you must remember that this study is useful for everyone, and especially for some categories of expectant mothers. High-risk groups include:

expectant mothers over the age of 35, regardless of previous experience of pregnancy and childbirth. This recommendation is associated with an increase in the number of possible chromosomal abnormalities during the onset of the aging process of the body;
women who have been diagnosed with a condition that threatens spontaneous miscarriage or miscarriage, frozen, non-developing pregnancy;
a history of infectious diseases (including influenza, ARVI during the first trimester);
parents with genetic disorders, women who, during previous pregnancies, had a high risk of genetic abnormalities, the presence of pathologies, or have children born with chromosomal abnormalities;
pregnant women forced to take medications that are restricted or prohibited for use during or immediately before gestation, certain types of vaccinations and medical procedures that briefly preceded pregnancy;
women whose pregnancy resulted from a close relationship;
women with bad habits: alcohol, drug addiction, etc.

A screening study does not pose a risk to the fetus or mother, so refusing diagnostics, which can reveal deviations that can be easily corrected at a given time, is at least unreasonable.

The study is carried out in public clinics free of charge. If you choose, you can undergo screening in any other clinic; if necessary, it is possible to repeat both the full study and one of its stages, if the timing of pregnancy allows.

What is included in the first perinatal screening?

Screening in the first trimester of pregnancy is limited to an ultrasound examination of the condition of the woman’s fetus and uterus, as well as a biochemical test of the pregnant woman’s blood, which determines the level of relevant hormones and the presence of certain markers.

The size of the fetus, the characteristics of the development of its body parts, bones, the presence of certain parts of the circulatory system in combination with the results of a blood test make it possible to confirm the correctness of the child’s development and the reaction of the mother’s body, or to suspect the possibility of some deviations.

How to prepare for the first screening?

Ultrasound examination of the fetus and uterus can be carried out using two methods: using a device with a transvaginal sensor or a transabdominal method of external examination through the surface of the peritoneum.

In the first case, preparation for the study consists of emptying the bladder immediately before the ultrasound; in the second, before the study it is necessary to fill the bladder, which will create the necessary darkening and contrast. The bladder should be filled approximately 30 minutes before the start of the study; the required volume of fluid is from 0.5 to 0.7 liters. It is preferable to drink non-carbonated drinking water and not visit the toilet, starting from 4 hours before the time of visiting a specialist until the end of the ultrasound.

During the procedure itself, the position of the fetus is an important factor. If the child lies in such a way that it is difficult to calculate the exact dimensions of some parts of the body, then the expectant mother may be asked to walk, bend over, tense and relax her stomach, imitate a cough, etc. At this time, it is sometimes possible to determine the sex of the unborn child, but for For a more accurate result, it is better to wait for the second ultrasound at a period above 20 weeks.

Blood biochemistry during screening of the first trimester should be carried out strictly after an ultrasound examination. The blood formula in the mother's body changes daily during pregnancy, and without correlation with the ultrasound date, a specialist will not be able to correctly interpret the analysis data.

For the most reliable results of a biochemical blood test, it is necessary to exclude all factors that may affect the functioning of various organs. Thus, preparation for the second stage of screening includes:

exclusion from the diet of foods that are potential allergens for all women (cocoa products, nuts, shellfish, citrus fruits, out-of-season vegetables and fruits) and identified allergens for pregnant women with a history of allergic reactions. It is necessary to notify a specialist about the presence of an allergy at the time of screening or shortly before it, this will allow a more accurate assessment of the test results. There is no need to talk about the need not to drink alcohol during pregnancy, but before screening this rule is especially important and applies even to small doses of alcohol on holidays;
The last meal should be 12 hours before blood sampling for testing, in the evening of the previous day. After getting up and before the analysis, you should not drink;
immediately before taking blood, you need to sit for 15-20 minutes, avoid stress and physical activity (jogging after the bus, climbing long stairs, etc.).

Failure to comply with the above rules may lead to distortions in test results, which may be incorrectly interpreted as a deviation in the development of the fetus or the course of pregnancy. Such unnecessary risks must be avoided.

Fetal parameters assessed by ultrasound during first trimester screening

During the ultrasound examination, the specialist evaluates the size of the fetus according to various indicators, as well as some important parameters of the child’s body at this period of development, features of the development and condition of the placenta and the mother’s uterus.

In the ultrasound results during the first screening, you can see the following designations:

KTR, or the length of the fetus from the crown to the tailbone: this is how the process of intrauterine development indicates the “growth” of the child, since the most characteristic position of the fetus - with legs bent and pulled to the chest, especially in the later stages - does not allow determining the length of the entire body. Full “height” can be roughly estimated based on the length of the femur bone, which, like the length of the shoulder and forearm bones, is an important indicator of fetal development;
OG is an indicator of the size of the fetal head, measured by circumference (calculated based on diameter);
BPR is an indicator of the bioparietal size of the head between the parietal bones. This indicator reflects both the development of the fetal head structures and, in later stages, allows us to make assumptions about the mother’s preferred method of delivery. With a large volume of the skull and a narrowed pelvis, a cesarean section will most likely be offered. The distance from the forehead to the back of the child’s head is also measured;
TVP is an indicator of the thickness of the nuchal space or cervical fold of the fetus, assessed only in the first trimester. By week 16, this formation is transformed into new organs, and during the first screening for this indicator, in combination with blood markers, the absence or increased likelihood of the presence of chromosomal disorders is diagnosed;
the thickness of the nasal bone as a probable indicator of the presence of genetic abnormalities is measured by ultrasound at 12-13 weeks; ultrasound at 11 obstetric weeks in most cases allows only to notice its presence and the beginning of its formation;
structural features of the brain, skull bones: this indicator describes how symmetrically and in accordance with the norm the skull and brain tissue of the fetus develop;
Heart rate, a measure of the heart rate or heartbeat, is assessed according to age-specific norms. Also, when examining the heart, if possible, the specialist examines the size and structural parts of the heart muscle. The location of the heart, stomach, large arteries and veins is also examined;
localization of the chorion (placenta), thickness of this organ. Later studies will also examine the presence and quantity of calcifications - inclusions indicating physiological aging of the placenta;
number of umbilical vessels;
volume and condition of amniotic fluid;
characteristics of the tone of the uterus and cervical pharynx.

Average values of basic parameters according to weeks of pregnancy:

Interpretation of the results of biochemical screening of the first trimester

The main indicators that specialists focus on when deciphering the results of a biochemical blood test at this stage are the level of human chorionic gonadotropin, the pregnancy marker hormone hCG, and plasma protein A, or PAPP-A.

The fetal membrane (chorion), which begins to form immediately after fertilization of the egg by the sperm, produces human chorionic gonadotropin on the very first day. However, this hormone reaches reference values for determining pregnancy no earlier than after 2 weeks. Highly sensitive rapid tests and blood tests for pregnancy determine the presence of this particular component.

In the first weeks of pregnancy, the level of human chorionic gonadotropin increases, doubling almost daily. The level of this hormone reaches its peak concentration at 11-12 weeks, then it decreases and stabilizes at insignificant levels.
High hCG in relation to the norm may indicate the following abnormalities and/or physiological conditions:

multiple pregnancy, in which the hormone is produced by several chorions;
maternal endocrinological diseases (diabetes mellitus) in history or developing during gestation;
manifestation of severe toxicosis in the first trimester;
chromosomal disorder - Down syndrome in the fetus.

A reduced level of human chorionic gonadotropin (hCG) relative to reference values may indicate the following disorders:

placental insufficiency;
presence of ectopic pregnancy;
increased risks of miscarriage and spontaneous abortion;
genetic disorder - Edwards syndrome in the fetus.

When assessing PAPP-A levels, only decreased values are significant. They may indicate a threat of miscarriage due to an inadequate response of the mother's immune system or poor functioning of the placenta, as well as some chromosomal abnormalities in the fetus.

Comprehensive interpretation of screening results

The first trimester screening results, after a full assessment of all indicators, will contain the following data:

risks of deviations associated with maternal age;
assessment and interpretation of maternal biochemical blood parameters;
the likelihood of the presence or occurrence of various diseases;
MoM value.

Based on the results of an ultrasound examination and a biochemical blood test, specialists bring the data together and assign the so-called MoM index (multiple of median). This coefficient is formed on the basis of variable indicators characteristic of the range of research results of healthy women with a normal pregnancy and a timely developing fetus.

The norms for the first screening range from 0.5 to 2.5 units for a singleton pregnancy, and up to 3.5 if two or more babies are expected.
After calculating the IOM, the results are entered into a program that takes into account all factors that influence the health of the mother and child and the course of pregnancy: age, height-to-weight ratio, some diseases (in particular, diabetes), the presence of bad habits (tobacco smoking), number of pregnancy fetuses, physiological or extracorporeal method of conception, etc.

Based on the evaluation of all data, the program provides a probable risk of genetic abnormalities in the fetus. The result is presented as a proportion of 1:1000 for several genetic diseases, expressing the risk of occurrence of a given syndrome in each specific case. An index of 1:380 or more is considered a positive result of a low risk of violations; an index below 1:380 means an increase in risk.

But this indicator is not a final diagnosis, but an assessment of probabilities. So, if a specialist’s conclusion contains an index of 1:70 for Down syndrome, this means that only 1 out of 70 women with similar results gives birth to a child with developmental disorders. In 69 cases, pregnancy proceeds without abnormalities and ends in the birth of a healthy child.

The following factors influence the distortion of results:

non-compliance with the rules of preparation for biochemical analysis;
outdated ultrasound equipment;
in vitro fertilization;
endocrinological disorders (diabetes mellitus of both types);
multiple pregnancy;
increased maternal body mass index (overweight).

What to do if the screening results are disappointing?

Many women are afraid to undergo the “first exam” in the life of the fetus, fearing both hearing negative news and hasty prescriptions and even pressure to terminate the pregnancy. If you have any doubts about the results, you can undergo additional screening, following the rules of preparation and alternation of ultrasound and biochemistry, and evaluate the condition and results as a whole.

In fact, “high risk” is diagnosed at rates between 1:250 and 1:380 for any syndrome, which means a slightly increased, but not necessarily, likelihood of a child having genetic abnormalities. With such indicators, it is recommended to lead a healthy lifestyle, regularly see a gynecologist and undergo genetic counseling.

In some cases, a genetic specialist may suggest undergoing additional examination for an accurate diagnosis (chorionic villus biopsy, amniocentesis, cordocentesis), on the basis of which recommendations for parents will be made.

From the moment of conceiving a child, every expectant mother begins to tune in to many tests, analyzes and medical consultations. No matter how frightening all this may be for pregnant women, without such research it is impossible to identify likely serious risks associated with the health of the fetus. Throughout the entire period, it is necessary to adhere to the entire prevention program, which is prescribed by the treating gynecologist.

It is important not to neglect the recommended tests. Biochemical screening is considered one of the most mandatory tests. Despite the unattractive name, this analysis is very useful for building a picture of the health of the unborn child.

What it is

Biochemical blood screening is a rather narrow-profile analysis. Applies to primary and secondary test categories. Detects signs of diseases such as hepatitis B and rubella. In the extended version, the analysis allows you to determine the presence of syphilis and HIV infection in the blood.

Nevertheless, the main function of screening is considered to be to identify the fetus’s predisposition to pathologies. Also, the results of the analysis clearly demonstrate how certain diseases will develop in the embryo in the future. In this regard, the attending physician builds a step-by-step program for the treatment or prevention of pathologies. Biochemical screening allows you to determine the Rh factor and blood type. These characteristics will be extremely useful in the future if the mother needs proper treatment. To prescribe serious hormonal drugs, it is important to know the Rh factor of the pregnant woman and her child.

An increased BPD may be a symptom of the presence of a brain tumor or hernia, or the development of hydrocephalus.

In the first case, the pregnancy is terminated, and treatment with antibiotics is prescribed for hydrocephalus.

A greatly reduced BPD of the embryonic head also does not bode well, as it is a symptom of brain underdevelopment. As a rule, such a pregnancy is terminated.

It includes another important indicator – the size of the nasal bone. This marker, like TVP, may be a sign of the development of Down syndrome in the embryo.

Despite the fact that prenatal examination in the early stages (10-11 weeks) does not allow assessing the size of the nasal bone, during this period it is still visualized on the screen.

Already at 12-13 weeks, a prenatal ultrasound should show that the nasal bone is normal; a size of at least 3 mm is considered normal.

Prenatal first biochemical screening involves examining the levels of two hormones, which is why it is also called a “double test”.

Biochemical screening helps to identify and determine the level of hCG in the blood of the expectant mother, as well as examine blood plasma for the presence and amount of protein (PAPP).

Both of these substances are present in the blood only in women carrying a child.

As soon as the first prenatal biochemical screening has been carried out, the decoding of the finished results is carried out taking into account the established standards:

the hCG level in the first trimester should be 0.5 - 2 MoM;
the level of PAP in the first trimester should be from weeks 9 to 13 – 0.17 – 6.01 mIU/ml.

A strong deviation from the established standards of a prenatal test may be a symptom of the development of Down or Edwards syndromes, but only a doctor can judge the presence of such pathologies, taking into account additional examinations.

Second trimester prenatal biochemical test

If a prenatal test in the 1st trimester can detect up to 95% of cases of chromosomal abnormalities, then a timely prenatal screening test in the second trimester is no less informative in this regard.

But the main purpose of the second prenatal examination is to detect neural tube defects and other fetal malformations, as well as to carry out calculations that subsequently make it possible to identify the risk of congenital hereditary or chromosomal diseases, among them:

Patau syndrome;
hereditary diseases Shershevsky-Turner syndrome and Smith-Opitz syndrome;
polyploidy.

As a rule, after the mother has undergone the first comprehensive examination, second trimester screening is prescribed either at the request of the future parents or as prescribed by a doctor in specific cases.

2nd trimester screening is carried out at 16–20 weeks. Assessment of biochemical blood parameters of the expectant mother is carried out at 16–18 obstetric weeks.

Before donating blood for analysis, a pregnant woman must have with her an ultrasound scan of the first trimester indicating the exact stage of pregnancy.

Before donating blood for a biochemical analysis, the doctor sending the pregnant woman for examination fills out the 2nd screening questionnaire with her, where she indicates the results of the ultrasound, the due date, the parameters of TVP and CRT.

All this is data from an ultrasound examination of the first trimester, since it is too early to do the second ultrasound at 16-18 weeks, it is carried out at 20-21 weeks.

The pregnant woman takes the completed questionnaire according to all the rules to the laboratory, where blood is taken for hCG, AFP and NEZ.

The main thing is to take the tests on an empty stomach, and on the eve of the procedure do not eat too salty, spicy or fatty foods, which can distort the results.

When the results of biochemical screening of the second trimester are ready, the doctor studies the information received and, comparing it with the established standards of the triple test, gives recommendations to the expectant mother or prescribes additional procedures.

AFP, hCG and free estriol

It is by the 16th week of pregnancy that an increased or decreased level of a-fetoprotein in the blood makes it possible to accurately identify a neural tube defect and other defects indicated in the following table.

HCG (human chorionic gonadotropin) is produced first by the membrane of the embryo, then by the placenta.

If the hormone is normal, then the pregnancy is proceeding safely, but if the prenatal biochemical test reveals abnormalities, then there are several reasons for this, which are given below in the table.

NEZ (unconjugated estriol, free) - the hormone is first produced by the placental membrane, then by the fetus itself. As pregnancy progresses, there is an increase in NEZ in the blood of the expectant mother.

A significant decrease or increase in the hormone is a symptom of a pregnancy disorder or fetal development pathology.

Deviations from the norm may be caused by the following reasons:

EZ – free estriol
Promoted	Demoted
Large fruit	Risk of miscarriage
Multiple pregnancy	Postmaturity of the fetus
Risk of premature birth (with a strong increase in EZ)	Intrauterine infection
	Down syndrome
	Neural tube development disorder
	Violation of the development of internal organs of the fetus
	The pregnant woman took medications prohibited in her situation
	Feto-placental insufficiency

Correct interpretation of the results is very important. If the second screening confirms that the data obtained is not within normal limits, you must definitely consult a doctor.

Prenatal second screening does not exclude the possibility of obtaining either false negative or false positive results.

Therefore, expectant mothers should not independently interpret the risks, which can, in the end, greatly affect their nervous system.

If the results of the second prenatal screening are strongly deviated from the norm, then this fact should not be considered a death sentence, at least until additional research is carried out.

Every pregnant woman faces screening in the 1st trimester, and then a second screening in the 2nd trimester. When I was pregnant for the first time, I was told that I needed to get screened. What it is and why was not explained in detail; I had to look for information on the Internet myself. After all, it is important to properly prepare for this study so that the results are as reliable as possible. But even careful preparation will not give you a 100% guarantee that the results will be correct.

Read in this article why screening in the 1st trimester, what studies this concept includes, how to prepare for them and how to decipher the results.

Screening - what is it?

Screening in the 1st trimester of pregnancy is a special examination of the fetus for developmental defects. Screening is carried out from 10 to 13 weeks. In the antenatal clinic, absolutely all pregnant women are told about the need for such research and given directions. But a pregnant woman may refuse screening. In this case, she will be asked to write a written refusal.

I had both screening tests done during my first pregnancy and I still remember how worried and nervous I was. Because I knew a case where a woman was told that she would have a child with Down syndrome, but she did not have an abortion. As a result, a completely healthy child was born. Can you imagine what she went through during these 9 months?

Unfortunately, there are also errors of the opposite nature. Screening cannot always predict the birth of a sick child.

The screening itself consists of two studies - ultrasound and blood donation from a vein for biochemistry. Ideally, you should have these two treatments done on the same day to get more accurate results.

It is most important to screen the following categories of women in the 1st trimester:

those who have had 2 or more miscarriages or premature births;
those who had a previously frozen pregnancy;
who have relatives or children with genetic diseases;
age over 35 years;
if a woman had a viral or bacterial infection in the early stages;
if the woman took medications that should not be taken by pregnant women;
if the pregnant woman is in a close family relationship with the child’s father;
who has a “harmful” job;
for alcohol, tobacco and drug addiction.

What pathologies are detected at the first screening.

During screening in the 1st trimester, studies are carried out to identify the following pathologies:

Down syndrome. This is a chromosomal pathology when the 21st pair of chromosomes has three chromosomes instead of two. This syndrome is not rare; 1 case occurs in 700 fetuses. The risk of developing this syndrome increases with maternal age.
Patau syndrome. This is also a chromosomal pathology when there is an additional copy of chromosome 13 in the cells. The birth rate of children with this syndrome is 1 in 7,000 or 10,000. Children born with this pathology in most cases die before the age of 1 year because they have very severe developmental anomalies.
Edwards syndrome. This is a chromosomal disease when there are three chromosomes in the 18th pair of chromosomes. With this pathology there are many different developmental defects. This syndrome occurs in 1 child in 5000-7000.
Smith-Opitz syndrome. This is a hereditary disease that is caused by gene mutations. This disrupts the metabolism of cholesterol, which is necessary for the embryo for the proper development of the brain, nervous system, limbs and other important functions. The incidence of the disease is 1 in 20,000-30,000.
Triploidy. This is a rare chromosomal abnormality. In this case, the fetus, instead of the required 46 chromosomes (23 from the father, 23 from the mother), has 69 chromosomes. In most cases, such pregnancies end in miscarriage; less often, children are born alive, but with multiple disorders.
De Lange syndrome. The cause of this disease is gene mutations. Damage to internal organs can vary in severity.
Omphalocele. This is a severe malformation when the child’s abdominal organs (intestines and liver) are located outside, in the umbilical cord, which is dilated.
Neural tube pathologies.
Timing of screening in the 1st trimester and preparation for it.

The first screening must be done from the beginning of the 10th week to the end of the 13th week. And it is best to do it at 11-12 weeks. The gynecologist will tell you the best moment, based on the date of your last menstruation.

The first screening after the 13th week can no longer be considered reliable.

Preparing for an ultrasound. This procedure can be done in two ways: transvaginally and abdominally.

The transvaginal method is considered more accurate than ultrasound through the abdomen. This ultrasound is performed with a special sensor, which is inserted into the vagina. In this case, a condom is put on the sensor, which is lubricated with a special gel. This ultrasound determines whether there is a threat of miscarriage or whether there is a threat of placental abruption. No special preparation is required for such an ultrasound; it is done on an empty bladder.

If you prefer to do an ultrasound abdominally (through the abdominal wall), you will have to fill the bladder. To do this, half an hour before the test, drink 0.5-1 liters of still water and do not go to the toilet. For ultrasound in the second trimester, you no longer need to do this. It is advisable that the intestines be empty. That is, you do not need to eat at least 4 hours before the ultrasound.

Preparing for blood collection.

In order for the result to be as accurate as possible, you need to adhere to important rules. First, blood is donated on an empty stomach. This means that you should not eat for at least 6 hours before this test. You can drink some water, but don't get carried away.

Second, you need to go on a special diet one or two days before taking this test. On this day you cannot eat anything smoked, fatty, fried, or spicy. And also exclude chocolate, citrus fruits, and seafood.

By the way, it is better to exclude chocolate, citrus fruits, and strawberries from the diet of pregnant women altogether, so that the child is not prone to allergies. You can’t eat fatty foods, because it will be impossible to get normal serum from your blood, and the money for biochemistry will be wasted.

You need to come to donate blood with the results of an ultrasound scan, because the indicators in the blood test are closely related to the stage of pregnancy. You will receive the biochemistry results in a week and a half.

Decoding the results of the first screening.

Ultrasound norms in the first trimester.

Coccygeal-parietal fetal size (CTF). The norm depends on the stage of pregnancy. See the table for the standards for this indicator.

Neck thickness (TCT). This indicator is considered very important when screening for genetic disorders.

A TVP size of more than 3 mm can be regarded as a risk of developing Down or Edwards syndrome.

Nasal bone.

This indicator is considered very important, because in Down syndrome this bone is not detected in the early stages.

Normally, at 10-11 weeks this bone is already detected on an ultrasound, but not measured. At 12-13 weeks, the nasal bone should be at least 3 mm. If this indicator is less than normal, and the collar zone is more, then this may indicate the development of Down syndrome.

Fetal heart rate (HR).

Biparietal size (BPR)- this is the distance between the parietal tubercles.

Also, ultrasound measures the size of internal organs, assesses the condition and placenta previa, and looks at the umbilical vessels. An ultrasound will determine the exact gestational age.

Interpretation of blood test results for hormones.

After the ultrasound, you will need to donate blood from a vein for hormones. Read here the norms for a biochemical blood test in the 1st trimester. This time the blood is examined for two markers - β-hCG (human chorionic gonadotropin) and PAPP-A (pregnancy-associated protein A).

Chorionic gonadotropin.

If the levels of this hormone reduced, then this indicates a pathology of the placenta or an increased risk of Edwards syndrome. Increased the amount of these hormones may be associated with the development of Down syndrome. And also this hormone will be more than normal during pregnancy with twins.

RARR-A. This is a protein that is produced by the placenta. The amount of these proteins increases with pregnancy.

Also, during a blood test, the MoM coefficient is calculated. Normally, this coefficient is 0.5-2.5 at this stage of pregnancy. If the pregnancy is twins, then MoM can be up to 3.5.

If MoM is below 0.5, this is interpreted as a risk of developing Edwards syndrome, MoM above 2.5 is a risk of developing Down syndrome.

How is the risk of congenital pathologies in the fetus calculated?

After passing the screening, you should be given the results of the examination. These results should indicate the risks for each individual syndrome. For example, Down syndrome - risk 1:380. This means that women with the same screening results give birth to 1 sick child per 380 healthy ones.

This calculation is made using a special computer program into which your ultrasound data, the results of a biochemical blood test, as well as age, individual characteristics of the body, concomitant diseases and pathologies, and harmful factors are entered. And taking all these parameters together, the program calculates the risks.

A risk of 1:250-1:380 is considered high. In this case, they are always referred to a geneticist for consultation. For an accurate diagnosis, parents will be asked to undergo additional tests: amniocentesis or chorionic villus biopsy. These studies can be life-threatening for the child (1% of children die after such an intervention). But after amniocentesis, they will tell you with almost a 100% guarantee whether the child is healthy or not.

If the risk of pathologies is low, then in the second trimester the pregnant woman will be sent for a second scheduled screening.

What influences screening results.

As I wrote above, screening results may be erroneous. There are factors that can affect the final result.

If a pregnant woman is obese, the amount of hormones will be increased, although this does not indicate fetal pathology. And if the expectant mother’s weight is too low, the amount of hormones will be less than normal.
With diabetes in the first trimester, the amount of hormones will be below normal. In this case, the results of the blood test will be unreliable.
If a woman is pregnant with twins, then she only undergoes an ultrasound, because the exact norms for hormones are unknown.
If pregnancy occurs as a result of IVF, the hCG level will be higher than normal, and PAPP will be lower.
The emotional state of the woman being examined can also be affected. Therefore, it is better not to think about the bad, but to tune in to good results and not worry.

Features of screening in the first trimester.

Ultrasound screening for Down syndrome.

With this disease, in 70% of cases in the first trimester the nasal bone is not visible. But you should know that sometimes even in healthy children this bone may not be detected. The collar area is more than 3 mm. Disruption of blood flow in the venous flow. Increased heart rate, enlarged bladder. The upper jaw is smaller than normal. Facial features are smoothed.

Edwards syndrome.

Heart rate is below normal. The nasal bone is not identified. One umbilical cord artery instead of two. An omphalocele is present (when some internal organs are externally located in the hernial sac).

Patau syndrome.

Brain development is impaired. Heart rate increased. Omphalocele. The size of the fetus is smaller than expected at this stage.

It is better to undergo first trimester screening in one place to get the most reliable results. Proper preparation for screening and a positive attitude also play an important role. Remember that screening is not a diagnosis. And in case of increased risks, only additional research will help establish the truth.

Prenatal screening examination of the first trimester consists of two procedures: ultrasound diagnostics and blood testing for the possibility of genetic pathologies of the fetus. There is nothing wrong with these events. The data obtained through an ultrasound procedure and a blood test are compared with the norm for this period, which makes it possible to confirm the good or identify the poor condition of the fetus and determine the quality of the gestation process.

For the expectant mother, the main task is to maintain good psycho-emotional and physical condition. It is also important to follow the instructions of the obstetrician-gynecologist leading the pregnancy.

Ultrasound is only one examination of the screening complex. To obtain complete information about the baby’s health, the doctor must check the expectant mother’s blood for hormones and evaluate the results of a general urine and blood test.

Standards for ultrasound diagnostics I screening

During the first prenatal screening in the first trimester, the ultrasound diagnostic doctor pays special attention to the anatomical structures of the fetus, clarifies the gestational age (gestation) based on comparison with the norm. The most carefully assessed criterion is the thickness of the collar space (TVP), because This is one of the main diagnostically significant parameters, which makes it possible to identify genetic diseases of the fetus. With chromosomal abnormalities, the nuchal space is usually expanded. Weekly TVP norms are given in the table:

When performing ultrasound screening in the first trimester, the doctor pays special attention to the structure of the facial structures of the fetal skull, the presence and parameters of the nasal bone. At 10 weeks it is already quite clearly defined. At 12 weeks, its size in 98% of healthy fetuses ranges from 2 to 3 mm. The size of the baby’s maxillary bone is assessed and compared with the norm, because a noticeable decrease in jaw parameters in relation to the norm indicates trisomy.

During the 1st screening ultrasound, the fetal heart rate (heart rate) is recorded and also compared with the norm. The indicator depends on the stage of pregnancy. Weekly heart rate norms are shown in the table:

The main fetometric indicators at this stage during the ultrasound procedure are the coccygeal-parietal (CP) and biparietal (BPR) dimensions. Their norms are given in the table:

Fetal age (week)	Average CTE (mm)	Average BPR (mm)
10	31-41	14
11	42-49	13-21
12	51-62	18-24
13	63-74	20-28
14	63-89	23-31

The first screening involves an ultrasound assessment of blood flow in the ductus venosus (Arantius), since in 80% of cases of its violation the child is diagnosed with Down syndrome. And only in 5% of genetically normal fetuses such changes are detected.

Starting from the 11th week, it becomes possible to visually recognize the bladder during ultrasound. At the 12th week, during the first ultrasound screening, its volume is assessed, since an increase in the size of the bladder is another evidence of the threat of developing trisomy (Down) syndrome.

It is best to donate blood for biochemistry on the same day as the ultrasound screening. Although this is not a mandatory requirement. Blood is drawn on an empty stomach. Analysis of biochemical parameters, which is carried out in the first trimester, is aimed at identifying the degree of threat of genetic diseases in the fetus. For this purpose, the following hormones and proteins are determined:

pregnancy-associated plasma protein-A (PAPP-A);
free hCG (beta component).

These indicators depend on the week of pregnancy. The range of possible values is quite wide and correlates with the ethnic content of the region. In relation to the average normal value for a given region, the level of indicators fluctuates within the following limits: 0.5-2.2 MoM. When calculating the threat and deciphering the data for analysis, not just the average value is taken, all possible corrections for the anamnestic data of the expectant mother are taken into account. Such an adjusted MoM makes it possible to more fully determine the threat of developing genetic pathology in the fetus.

A blood test for hormones must be performed on an empty stomach and is often prescribed on the same day as the ultrasound. Thanks to the availability of standards for hormonal blood characteristics, the doctor can compare the test results of a pregnant woman with the norms and identify a deficiency or excess of certain hormones

HCG: risk assessment

In terms of information content, free hCG (beta component) is superior to total hCG as a marker of the risk of fetal genetic abnormalities. The beta-hCG norms for a favorable course of gestation are shown in the table:

This biochemical indicator is one of the most informative. This applies to both identifying genetic pathology and marking the course of the gestation process and changes occurring in the body of a pregnant woman.

Standards for pregnancy-associated plasma protein-A

This is a specific protein that the placenta produces throughout the gestational period. Its growth corresponds to the period of pregnancy development and has its own standards for each period. If there is a decrease in the level of PAPP-A in relation to the norm, this is reason to suspect the threat of developing a chromosomal abnormality in the fetus (Down and Edwards disease). The norms for PAPP-A indicators during normal gestation are shown in the table:

However, the level of protein associated with pregnancy loses its informative value after the 14th week (as a marker of the development of Down's disease), since after this period its level in the blood of a pregnant woman carrying a fetus with a chromosomal abnormality corresponds to the normal level - as in the blood of a woman with healthy pregnancy.

Description of the first trimester screening results

To evaluate the results of screening I, each laboratory uses a specialized computer product - certified programs that are configured for each laboratory separately. They make a basic and individual calculation of the threat indicators for the birth of a baby with a chromosomal abnormality. Based on this information, it becomes clear that it is better to carry out all tests in one laboratory.

The most reliable prognostic data are obtained by undergoing the first prenatal screening in the first trimester in full (biochemistry and ultrasound). When deciphering data, both indicators of biochemical analysis are considered in combination:

low values of protein-A (PAPP-A) and elevated beta-hCG – a risk of developing Down syndrome in a child;
low levels of protein-A and low beta-hCG are a threat to Edwards disease in the baby.
There is a fairly accurate procedure to confirm a genetic abnormality. However, this is an invasive test that can be dangerous for both mother and baby. To clarify the need to use this technique, ultrasound diagnostic data are analyzed. If there are echo signs of a genetic abnormality on an ultrasound scan, the woman is recommended to undergo invasive diagnostics. In the absence of ultrasound data indicating the presence of a chromosomal pathology, the expectant mother is recommended to repeat the biochemistry (if the period has not reached 14 weeks), or wait for the indications in the next trimester.

Chromosomal disorders of fetal development are most easily identified using a biochemical blood test. However, if the ultrasound does not confirm the fears, it is better for the woman to repeat the study after a while, or wait for the results of the second screening

Risk assessment

The information obtained is processed by a program specially created to solve this problem, which calculates the risks and gives a fairly accurate forecast regarding the threat of developing chromosomal abnormalities of the fetus (low, threshold, high). It is important to remember that the resulting transcript of the results is only a forecast, not a final verdict.

Quantitative expressions of levels vary in each country. For us, a value of less than 1:100 is considered a high level. This ratio means that for every 100 births (with similar test results), 1 child is born with a genetic pathology. This degree of threat is considered an absolute indication for invasive diagnostics. In our country, the threshold level is considered to be the risk of having a baby with developmental defects in the range from 1:350 to 1:100.

The threshold level of threat means that the child may be born sick with a risk of 1:350 to 1:100. At a threshold level of threat, the woman is sent to see a geneticist, who gives a comprehensive assessment of the data obtained. The doctor, having studied the parameters and medical history of the pregnant woman, identifies her in the risk group (with a high or low degree). Most often, the doctor recommends waiting until the second trimester screening test is performed, and then, having received a new threat calculation, come back for an appointment to clarify the need for invasive procedures.

The information described above should not frighten expectant mothers, and there is also no need to refuse to undergo first trimester screening. Since most pregnant women have a low risk of carrying a sick baby, they do not require additional invasive diagnostics. Even if the examination showed poor condition of the fetus, it is better to find out about it in a timely manner and take appropriate measures.

If research has revealed a high risk of having a sick child, the doctor must honestly convey this information to the parents. In some cases, invasive research helps clarify the situation with the fetus's health. If the results are unfavorable, it is better for the woman to terminate the pregnancy early in order to be able to bear a healthy child

If unfavorable results are obtained, what to do?

If it so happens that the analysis of the screening examination indicators of the first trimester revealed a high degree of threat of having a child with a genetic anomaly, first of all, you need to pull yourself together, since emotions negatively affect the gestation of the fetus. Then start planning your next steps.

First of all, it is unlikely to be worth the time and money to undergo re-screening at another laboratory. If the risk analysis shows a ratio of 1:100, you cannot hesitate. You should immediately contact a geneticist for advice. The less time is lost, the better. With such indicators, a traumatic method of confirming the data will most likely be prescribed. At 13 weeks, this will be an analysis of chorionic villus biopsy. After 13 weeks, it may be recommended to perform a cordo- or amniocentesis. Analysis of chorionic villus biopsy provides the most accurate results. The waiting period for results is about 3 weeks.

If the development of chromosomal abnormalities of the fetus is confirmed, the woman will be recommended to have an artificial termination of pregnancy. The decision is, of course, up to her. But if the decision is made to terminate the pregnancy, then the procedure is best performed at 14-16 weeks.

1st trimester screening is a diagnostic test. It is performed on a pregnant woman who is at risk from 10 to 14 weeks.

Risk determination Biochemical Ultrasound
about the state of health within development
viewing plan shot

This examination allows you to determine with high accuracy whether there is a high risk of having a defective child. It consists of two parts: first you donate blood from a vein, then you undergo an ultrasound. Based on these studies, taking into account the characteristics of each individual woman and how her pregnancy proceeds, a geneticist can already draw a certain conclusion.

1st trimester screening is carried out starting from the 11th to 13th week of pregnancy. Women at risk include the following:

those who are closely related to the child's father;
who had two or more preterm births;
history of previously frozen pregnancies;
gave birth to a stillborn child, or the woman suffered a viral or bacterial disease during pregnancy;
there are people in the family who suffered from genetic diseases and pathologies;
the family already has a child who has pathologies, for example, Down syndrome, Patois, etc.;
was treated with medications that can harm the fetus;
woman over 35 years of age;
desire to find out about the presence of pathology in both parents.

This allows you to find out about the condition of the fetus in the early stages

Why is screening done in the first trimester?

The length of the embryo and the size of the head are assessed.
The first examination shows the symmetry of the cerebral hemisphere and the presence of the necessary structures at a given time.
Tubular bones, humerus, femur, tibia, etc. are examined;
They check whether the organs are in their place (stomach, heart, their size, etc.);
This is a safe way to determine possible chromosomal abnormalities of the fetus;
Pathologies of the CNS primordia are determined;
The presence of an umbilical hernia is determined.

It is better to make diagnostics during this period, because errors in calculations reduce the correctness and accuracy of the results. Your attending physician should study everything thoroughly and calculate the time from the last day of menstruation and order the first fetal examination.

What does research mean?

Perinatal means prenatal. Therefore, the procedures and related terms prenatal screening (if necessary, it can be done in the 1st trimester) are procedures that allow you to clarify the condition of the intrauterine fetus. Since a person’s life begins from the moment of conception, various health problems may arise even before birth.

In order to determine the health status of the fetus, methods such as:

ultrasonography;
cardiotocography;
biochemical research.

Of course, perinatal diagnostic methods do not border on the risk of pregnancy complications, but still they are used only when there are all indications for this. Often these are women who are at risk.

Definition of what biochemical screening is - this is a set of diagnostic procedures that are performed (1st trimester) on the basis of venous blood. Special hormones are determined that are a marker of chromosomal pathologies in the fetus. Thanks to this examination, it is determined how high the risk of developmental defects is in a growing fetus. It is carried out together with ultrasound examination at the same time.

Biochemical screening

Studies conducted as part of perinatal screening are safe. They do not have any negative effect on pregnancy or the fetus; they are done for all pregnant women. Usually carried out (from 10 - 14 weeks), and in the second trimester (16 - 20 weeks of pregnancy).

Biochemical screening, which is done in the first trimester, consists of several studies. The concentration of markers is determined to assess the risk of chromosomal abnormalities of the embryo. The most optimal periods for conducting research are from 11 to 13 weeks.

The results of biochemical screening are pregnant women who have been identified as having a high risk of having a child with NTDs and chromosomal diseases of the unborn baby. If the results of the analysis in the 1st trimester are deciphered and the presence of pathologies is confirmed, if there is a high level of NTD, an ultrasound scan and additional tests are prescribed. NTD is the probability that there may be a defect in the fusion of the neural tube in the embryo.

Stages of diagnostics

A woman who is going for screening is worried about how the examination will go. What kind of pain will there be? The fear of harming the fetus remains. You will not experience any severe pain, except for the injection to draw blood. But the most exciting stage is waiting for the results.

The examination will include such points - if this is the first trimester, such as a blood test to check hormones and an ultrasound examination. At the second stage, they are usually limited to blood sampling only.

How is the procedure performed and how to prepare for screening in the 1st trimester:

you don’t need to drink too much before you are going to take hormones, 100 ml on an empty stomach is enough;
Eating is also not recommended; if you do the examination on a full stomach, the results will be incorrect and blurred;
An ultrasound is performed on a full bladder, and before the procedure you must drink at least a liter of water.

First, they do an ultrasound. It is performed transvaginally or abdominally:

in the first case, no preparation is needed; a special sensor will be inserted directly into the vagina;
in the second case, the sensor will be used to examine the outside of the abdomen and, as already mentioned, the bladder should be full.

You shouldn't go to the toilet three to four hours before. After you have had an ultrasound, you go for a blood test with these results. Before taking it, it is recommended to follow a diet that excludes chocolate, seafood, citrus fruits, meat, and fatty foods from the diet (preferably several days in advance). They will talk to you before donating blood.

Ultrasonography

The results will be ready in about a few weeks. It is necessary to decipher the results only in the presence of a doctor, so that he tells everything correctly, and so that you do not worry in advance.
The doctor monitors for the presence of infections (syphilis, HIV infections, hepatitis B and C, etc.), diseases that can subsequently cause harm to the development of the fetus. Determines the risk of developing pathologies in order to provide the necessary treatment in a timely manner.

Examination result standards

Screening is the process of collecting all data about the health status of the unborn child and mother. The concept of norm in such studies is relative. If there are slight deviations in the indicators, this does not mean the presence of pathologies. It is possible that what is normal for one embryo at 11 weeks, for another it may be an anomaly, the characteristics of the growth and weight of the fetus are taken into account.

Standard ultrasound screening results, which show in the 1st trimester, close to normal in terms of timing:

the coccygeal-parietal dimensions (CPD) of the fetus at the beginning of the 10th week should be from 33 to 41 mm, on the sixth day of the 10th week from 41 to 49 mm;
at week 11 - from 42 to 55 mm on the first day, on the sixth day from 49 to 58 mm;
at the 12th week of the term this size should be from 51 to 59 mm, on the sixth day from 62 to 73 mm;
From 10 – 14 weeks – the thickness of the collar zone should be from 2.5 to 4.5 mm.

There are indicators that should alert specialists in case of deviation:

folds in the collar part, at 12 weeks - this may indicate Down syndrome in the fetus;
any change in the structure of the heart or large vessels may indicate a heart defect;
increased hyperechogenicity of the medulla may indicate cystic dysplasia or polycystic kidney disease.

Experts focus on a lot of things and try to identify the slightest risks in order to exclude this or that disease. In any case, screening will allow you to determine the type of defect and tell you how to behave in a given situation.

Collection of all data

All studies conducted are individual. Only on the basis of all the data about your pregnancy can you draw a conclusion regarding a particular diagnosis.

Doctors may decide to terminate the pregnancy, but parents may insist on the birth, then doctors help carry the child to term and help deliver the baby with minimal losses.

All pregnant women who are registered at 12 weeks should undergo this procedure. But this is a voluntary matter; no one will force you to undergo the procedure.

Examinations in clinics in St. Petersburg.

Where can you get an ultrasound screening examination in Moscow?

Clinic name	Clinic address	Service cost
Polyclinic of the Research Institute of Physical and Chemical Medicine of the Federal Medical and Biological Agency of Russia	st. Malaya Pirogovskaya, 1a	Screening ultrasound in the 1st trimester of pregnancy – 1800 rubles; Screening ultrasound of the fetus in the 2nd and 3rd trimester – 2500 rubles.
Moscow Medical Clinic "Women's Health Center"	Kutuzovsky prospect, 33	Screening ultrasound in the first trimester – 3500 rubles; Screening ultrasound in the 2nd trimester – 4500 rubles; Screening in the 3rd trimester – 5000 rubles.
Fetal Medicine Center	st. Myasnitskaya, 32	Screening ultrasound 1st trimester – 4800 rubles; Second trimester – 5800 rubles; 3rd trimester – 5200 rubles.

Where can similar research be done in other cities?

Name of the clinic	Clinic address	Service cost
"Harmony" Medical Center for Family Planning and Human Reproduction	Ekaterinburg, st. Rodonitovaya, 1	Ultrasound screening up to 11 weeks – 1200 rubles; After 11 weeks – 1600 rubles.
Alpha Health Center	Nizhny Novgorod, st. Maxim Gorky, 48, bldg. 50 Intersection of Maxim Gorky and Malaya Yamskaya streets, near the metro bridge	Ultrasound screening costs 2500 rubles.
Medical Center "Samara School of Ultrasound"	Samara, st. Mira, 12	Examination of a singleton pregnancy in the 1st trimester – 1800 rubles; Examination 2nd and 3rd trimester – 3900 rubles.

They help identify the risk of chromosomal diseases in a child before birth. In the first trimester of pregnancy, an ultrasound and biochemical blood test for hCG and PAPP-A are performed. Changes in these indicators may indicate an increased risk of Down syndrome in the unborn child. Let's see what the results of these tests mean.

For what period?

1st trimester screening is done from 11 weeks to 13 weeks and 6 days (the period is calculated from the first day of the last menstrual period).

Signs of Down syndrome on ultrasound

If a child has Down syndrome, then already at 11-13 weeks the ultrasound specialist can detect signs of this disease. There are several signs that indicate an increased risk of Down syndrome in a child, but the most important one is something called Collar Space Thickness (TCT).

The thickness of the nuchal space (TN) has synonyms: thickness of the cervical fold, cervical fold, nuchal space, cervical transparency, etc. But all these terms mean the same thing.

Let's try to figure out what this means. In the picture below you can see a picture taken during the TVP measurement. The arrows in the picture show the neck fold itself, which is to be measured. It has been noticed that if a child’s cervical fold is thicker than 3 mm, then the risk of Down syndrome in the child is increased.

In order for ultrasound data to be truly correct, several conditions must be met:

Ultrasound of the first trimester is performed no earlier than 11 weeks of pregnancy (from the first day of the last menstruation) and no later than 13 weeks and 6 days.
The coccygeal-parietal size (CPR) must be at least 45 mm.
If the position of the baby in the uterus does not allow you to adequately assess TVP, then the doctor will ask you to move, cough, or lightly tap on the stomach so that the baby changes position. Or the doctor may advise you to come for an ultrasound a little later.
The measurement of TVP can be carried out using ultrasound through the skin of the abdomen, or through the vagina (this depends on the position of the child).

Although the thickness of the nuchal translucency is the most important parameter in assessing the risk of Down syndrome, the doctor also takes into account other possible signs of abnormalities in the fetus:

The nasal bone is normally detected in a healthy fetus after the 11th week, but is absent in approximately 60-70% of cases if the child has Down syndrome. However, in 2% of healthy children, the nasal bone may not be detected on ultrasound.
The blood flow in the ductus venosus (Arantius) should have a certain appearance, which is considered normal. In 80% of children with Down syndrome, blood flow in the Arancia duct is impaired. However, 5% of healthy children may also exhibit such abnormalities.
Reduced maxillary bone size may indicate an increased risk of Down syndrome.
An increase in bladder size occurs in children with Down syndrome. If the bladder is not visible on ultrasound at 11 weeks, then this is not scary (this happens in 20% of pregnant women at this stage). But if the bladder is not noticeable, then the doctor may advise you to return for a repeat ultrasound in a week. At 12 weeks, the bladder becomes noticeable in all healthy fetuses.
A rapid heartbeat (tachycardia) in the fetus may also indicate an increased risk of Down syndrome.
The presence of only one umbilical artery (instead of two normally) increases the risk of not only Down syndrome, but also other chromosomal diseases (Edwards syndrome, etc.)

Norm of hCG and free β-hCG subunit (β-hCG)

HCG and free β (beta) subunit of hCG are two different indicators, each of which can be used as a screen for Down syndrome and other diseases. Measuring the free β-subunit of hCG can more accurately determine the risk of Down syndrome in an unborn child than measuring total hCG.

The norms for hCG depending on the length of pregnancy in weeks can be found here: http: //www.mygynecologist.ru/content/analiz-krovi-na-HGC.

Norms for the free β-subunit of hCG in the first trimester:

9 weeks: 23.6 – 193.1 ng/ml, or 0.5 – 2 MoM
10 weeks: 25.8 – 181.6 ng/ml, or 0.5 – 2 MoM
11 weeks: 17.4 – 130.4 ng/ml, or 0.5 – 2 MoM
12 weeks: 13.4 – 128.5 ng/ml, or 0.5 – 2 MoM
13 weeks: 14.2 – 114.7 ng/ml, or 0.5 – 2 MoM

Attention! Norms in ng/ml may vary between laboratories, so the data provided is not final, and you should always consult your doctor. If the result is indicated in the MoM, then the standards are the same for all laboratories and for all analyses: from 0.5 to 2 MoM.

What if the HCG is not normal?

If the free β-subunit of hCG is higher than normal for your stage of pregnancy, or exceeds 2 MoM, then the child has an increased risk of Down syndrome.

If the free beta subunit of hCG is below normal for your gestational age, or less than 0.5 MoM, then the baby has an increased risk of Edwards syndrome.

Norm PAPP-A

PAPP-A, or “pregnancy-associated plasma protein A” as it is called, is the second indicator used in the biochemical screening of the first trimester. The level of this protein constantly increases during pregnancy, and deviations in the level may indicate various diseases in the unborn child.

The norm for PAPP-A depending on the stage of pregnancy:

8-9 weeks: 0.17 – 1.54 mU/ml, or from 0.5 to 2 MoM
9-10 weeks: 0.32 – 2.42 mU/ml, or from 0.5 to 2 MoM
10-11 weeks: 0.46 – 3.73 mU/ml, or from 0.5 to 2 MoM
11-12 weeks: 0.79 – 4.76 mU/ml, or from 0.5 to 2 MoM
12-13 weeks: 1.03 – 6.01 mU/ml, or from 0.5 to 2 MoM
13-14 weeks: 1.47 – 8.54 mU/ml, or from 0.5 to 2 MoM

Attention! The norms in mIU/ml may vary between laboratories, so the data provided is not final, and you should always consult your doctor. If the result is indicated in the MoM, then the standards are the same for all laboratories and for all analyses: from 0.5 to 2 MoM.

What if PAPP-A is abnormal?

If PAPP-A is below normal for your gestational age, or less than 0.5 MoM, then the baby has an increased risk of Down syndrome and Edwards syndrome.

If PAPP-A is higher than normal for your gestational age, or exceeds 2 MoM, but other screening indicators are normal, then there is no cause for concern. Studies have shown that in the group of women with elevated levels of PAPP-A during pregnancy, the risk of diseases in the fetus or pregnancy complications is no higher than in other women with normal PAPP-A.

What is risk and how is it calculated?

As you may have already noticed, each of the biochemical screening indicators (hCG and PAPP-A) can be measured in MoM. MoM is a special value that shows how much the obtained analysis result differs from the average result for a given stage of pregnancy.

But still, hCG and PAPP-A are affected not only by the duration of pregnancy, but also by your age, weight, whether you smoke, what diseases you have, and some other factors. That is why, in order to obtain more accurate screening results, all of its data are entered into a computer program that calculates the risk of diseases in a child individually for you, taking into account all your characteristics.

Important: to correctly calculate the risk, it is necessary that all tests are taken in the same laboratory in which the risk is calculated. The risk calculation program is configured for specific parameters, individual for each laboratory. Therefore, if you want to double-check your screening results in another laboratory, you will need to take all the tests again.

The program gives the result in the form of a fraction, for example: 1:10, 1:250, 1:1000 and the like. The fraction should be understood as follows:

For example, the risk is 1:300. This means that out of 300 pregnancies with indicators like yours, one child will be born with Down syndrome and 299 healthy children.

Depending on the resulting fraction, the laboratory issues one of the following conclusions:

The test is positive – there is a high risk of Down syndrome in the child. This means that you need a more thorough examination to clarify the diagnosis. You may be recommendedand chorionic villus sampling or amniocentesis.
The test is negative – the child has a low risk of Down syndrome. You will need a passand second trimester screening, but no additional testing is needed.

What should I do if I am at high risk?

If, as a result of screening, you have been found to have a high risk of having a child with Down syndrome, then this is not a reason to panic, much less terminate the pregnancy. You will be referred for a consultation with a geneticist, who will once again look at the results of all examinations and, if necessary, recommend undergoing examinations: chorionic villus sampling or amniocentesis.

How to confirm or refute screening results?

If you think that the screening was carried out incorrectly for you, then you can repeat the examination in another clinic, but for this you will need to retake all the tests and undergo an ultrasound. This will be possible only if the gestational age at this time does not exceed 13 weeks and 6 days.

The doctor says I need to have an abortion. What to do?

Unfortunately, there are situations when a doctor persistently recommends or even forces an abortion based on screening results. Remember: no doctor has the right to do such actions. Screening is not a definitive method for diagnosing Down syndrome and, based solely on poor results, there is no need to terminate the pregnancy.

Say that you want to consult with a geneticist and undergo diagnostic procedures to detect Down syndrome (or another disease): chorionic villus sampling (if you are 10-13 weeks pregnant) or amniocentesis (if you are 16-17 weeks pregnant).

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