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The first screening during pregnancy - the timing and what shows

Modern methods of examinations during pregnancy stipulate that the expectant mother should thrice get screened - once in each of the trimesters. And although the term itself is a bit intimidating with its unusual “frightening” medical name, there is nothing alarming or unusual about this. Screening is just a general comprehensive examination of the pregnant woman and the fetus to determine various indicators and identify possible deviations.

The duration of the first trimester is 13 weeks, towards the end of this period, the first screening is prescribed, during which the woman must undergo an ultrasound scan of the fetus (ultrasound) and pass the necessary tests.


As a rule, screening of the first trimester is prescribed 11-13 weeks of pregnancy. By this time the main systems and organs of the fetus are already formedtherefore, the doctor has the opportunity to assess the development of the future baby and identify possible violations in time.

importantAt this time, it is already possible to determine the presence of most genetic and chromosomal abnormalities: for example, Down syndrome, nervous system defects.

Types of research

In the process of screening in the first trimester of pregnancy, the following types of surveys are conducted:

  • Ultrasound examination of the fetus (ultrasound) - can be performed both transvaginally (by inserting the sensor into the vagina) and by the abdominal method (through the skin of the abdomen).
  • Biochemical blood test from a vein. Taking analysis is performed in the laboratory. A 10 ml blood sample is sufficient for the test.

informationThese types of examinations are desirable for all pregnant women. If there are indications and with the consent of the woman, additional procedures can be performed: for example, a biopsy of chorionic villi.

Screening preparation

The first screening during pregnancy requires careful preparation and compliance with a number of requirements and recommendations. With the passage of subsequent surveys in the second and third trimesters, the list of preparatory activities will become much smaller.

Before conducting the first screening screen, a woman should do the following:

  • during the day before the survey, to abandon the use of potentially allergenic products (chocolate, citrus, seafood, etc.),
  • refrain from fried and fatty foods,
  • to refrain from breakfast on the eve of the survey until blood is taken for analysis,
  • in preparation for abdominal ultrasound (through the abdomen), fill the bladder with fluid, after drinking 0.5 liters of water without gas for half an hour before the examination.

informationIn addition, it is desirable to perform the usual hygienic procedures, while eliminating the use of flavored cosmetics or hygiene products.

Regulatory Values

With the passage of the first screening special attention payon the following indicators and their compliance Recommended standard values:

  • Thickness of collar space (TVP) - is determined during the passage of ultrasound. Required for early diagnosis of Down syndrome. Normally, this indicator should be from 1.5 to 2.2 mm - at the 10th week of pregnancy, from 1.6 to 2.4 mm - at the 11th week, from 1.6 to 2.5 mm - at the 12th week, from 1.7 to 2.7 mm - at week 13.
  • Kopchik-parietal size (KTR) - also determined by ultrasound. The standard value of this parameter ranges from 33 to 49 mm - at week 10, from 42 to 58 mm - at week 11, from 51 to 83 mm - at week 12 of gestation.
  • Nasal Bone Assessment - along with the definition of TBI, is an indicator that allows for the timely diagnosis of Down syndrome. At 10-11 weeks, this figure is not yet estimated, at 12 and 13 weeks the size of the bone should be at least 3 mm.
  • Heart rate (HR) - this figure largely depends on the duration of the screening: at week 10 - from 161 to 179 beats per minute, at week 11 - from 153 to 177 beats / min, at week 12 - from 150 to 174 beats / min, by 13 week - from 147 to 171 beats / min.
  • Biparietal size (BPR) - allows you to estimate the size of the head of the fetus. Normally, this figure is: at week 10 - 14 mm, at week 11 - 17 mm, at week 12 - at least 20 mm, at week 13 - 26 mm.
  • The level of human chorionic gonadotropin (hCG) in the blood of a woman should be: at week 10 - from 25.8 to 181.6 ng / ml, at 11 weeks. - from 17.4 to 130.3 ng / ml, for 12 weeks. - from 13.4 to 128.5 ng / ml, and at week 13 - from 14.2 to 114.8 ng / ml.

informationIn addition, other parameters are determined during screening: on ultrasound, the development of various organs and systems of the fetus; in the analysis of blood, the level of glucose, protein A, associated with pregnancy (PAPP-A), etc.

Deviation from the norm

In the process of deciphering the results of ultrasound and blood tests, the doctor compares them with the standard values ​​and calculates the degree of risk. This determines the coefficient showing actual value deviationfrom some calculated value. When calculating the specified value, the doctor divides the actual figure by the average value of the median determined for this region and this period of pregnancy. The result is sometimes denoted by the abbreviation "MoM":

  • The rate at the first screening is from 0.5 to 2.5.. In the ideal case, the value of the indicator is 1.
  • If MoM level in relation to hCGis less than 0.5, this indicates an increased risk of developing Edwards syndrome. If this ratio exceeds 2.5, then the risk of Down Syndrome is high.

A generalized risk coefficient is then determined for the most serious chromosomal abnormalities. For example, the indicator 1: 500 in relation to Down syndrome means that one woman out of 500 pregnant women with similar indicators had a child with a similar ailment.

dangerouslyThe results of the first screening are considered bad if the generalized indicator is in the range from 1: 250 to 1: 380, and the results of the hormone content are below 0.5 or above 2.5 median indicators.

Possible false positive result screening in the following cases:

  • in the presence of twins,
  • with future mother's obesity,
  • with diabetes and other endocrine disorders.

Even a psychological attitude can significantly distort the results, because the level of hormones largely depends on the sense of stability and comfort of the pregnant woman, so you should feel calm and confident during any visit to a medical institution.

additionallyWhen receiving undesirable results of the survey, you should not despair, because the child can be completely healthy, despite the high risk of having a disease.

In this case recommended to visit specialist genetics and, possibly, to undergo additional examinations (amniocentesis, chorionic villus biopsy, cordocentesis).

Glucose tolerance test during pregnancy: which shows how to take

Hello, dear friends! Which of you is familiar with the first screening? I remember the first time my friend passed it. According to the results, he showed a bunch of sores and terrible pathologies to her still unborn baby. After that there was a sea of ​​tears, experiences and repeated studies. All was resolved in the end is good.

No, she was not given any magic pills. They simply explained that it should be carried out at a certain time. I did a little sooner or later - and distortion of the facts, and with them the terrible "diagnoses" can not be avoided. That is why I decided to write about it. So, the first screening during pregnancy - the timing, results, rates and deviations. Sit back, we begin!

1. What is the first screening

The first screening, or screening for the first trimester, is a comprehensive study that aims to identify pathologies of fetal development.

Most often it is Down syndrome, Edwards syndrome, and developmental disorders of the nervous system, which can lead to disability or non-viability of the future baby.

It consists of two stages - blood donation from a vein and ultrasound.

Lastly, by the way, it can be both transvaginal (when a sensor is inserted into the vagina) and abdominal (when the doctor examines the fetus through the skin of the abdomen).

2. When and to whom do the first screening

How long does this study take? Ideally at 11-13 weeks pregnancy, when all organs and systems of the fetus are formed.

It is worth noting that previously he was appointed only to women who were at risk, namely:

  • had children with genetic diseases
  • worked in hazardous production
  • took medications incompatible with the life of the fetus or threatening its health,
  • had genetic pathologies in the family,
  • gone through miscarriage or missed abortion
  • have not reached the age of 18 or crossed the line of a 35-year-old. As a rule, during this period, they either increase the risk of developing fetal abnormalities, or reduce the chances of carrying a baby.

In the last decade, the first screening is recommended to do absolutely everything. This is explained on the one hand by environmental degradation or the presence of bad habits in future parents. On the other hand, it is possible to identify pathologies in a timely manner, conduct additional diagnostics, such as a biopsy of the chorionic villi (what a geneticist will tell you), and start treatment. According to the doctors, in most cases it ends successfully.

3. How to prepare for the first screening.

The process of preparing for such a survey can be divided into two stages:

  1. The first is a set of activities that need to be carried out in advance. Simply put, it is in compliance with a special diet.
  2. The second includes small tricks that will allow doctors to get the most accurate results.

In this way, 1-3 days before screening a woman is better to refuse from:

  • typical allergens (chocolate, citrus, seafood),
  • fried and overly fatty foods
  • meat (the day before the study).

Immediately before the first screening ultrasound abdominal way to fill the bladder. You can do this by drinking 0.5 liters of water half an hour before the procedure. In the case of the transvaginal way, no special preparation is required.

Of course, you need to take blood from a vein on an empty stomach. In addition, doctors advise on the day of the study to abandon the use of cosmetics with fragrances and flavors when performing conventional hygiene procedures.

How is the first screening done?

The first part - the usual ultrasound. The second part is a blood test. The blood is taken in the laboratory, but not more than 10 ml. This volume is enough to assess the level of hormones with the help of special markers.

4. Regulatory indicators at the first screening

What does such a study show? Much, but most importantly, it gives a lot of useful information.

  • the first screening allows you to identify the location of the fetus in the uterus and, thus, to exclude ectopic pregnancy,
  • as accurately as possible to name the number of fruits
  • listen to the future heartbeat of the future baby, assessing the chances of its viability,
  • control the process of primordia of internal organs.

Meanwhile, spend it not only for the sake of it. On the first ultrasound screening The specialist searches for specific indicators and checks them for compliance.

  1. KTR - this is the coccyx-parietal size, which can vary from 33 to 49 mm (for a period of 10 weeks), 42 to 58 mm (11 weeks), 51 to 83 mm (12 weeks).
  2. TVP - the thickness of the collar space, which allows to determine the presence of Down syndrome. Ideally, it is 1.5 - 2.2 mm at week 10, 1.6 - 2.4 mm at week 11, 1.6 - 2.5 at week 12, 1.7 - 2.7 mm at week 13 .
  3. Heart rate - heart rate. Normally, at week 10, it should be 161 - 179 beats per minute, 153 - 177 beats / min at week 11, 150 - 174 beats / min at week 12, 147 - 171 beats / min at week 13.
  4. BPR - bipariented size, which shows the size of the fetal head and is 14 mm at 10 weeks, 17 mm at 11 weeks, from 20 mm at 12 weeks, 26 mm at 13 weeks.
  5. Nasal bone, which also indicates the presence of Down syndrome and at 12 - 13 weeks in the norm is not less than 3 mm. Rate it previously impossible.

In parallel with the decoding of the data obtained at the first screening, the placenta is examined to determine its condition, maturity, and method of attachment to the uterine wall.

Blood chemistry shows:

  1. HCG - the level of human chorionic gonadropine, which ideally should show 25.8 - 181.6 ng / ml at 10 weeks, 17.4 - 130.3 ng / ml at 11 weeks, 13.4 - 128.5 ng / ml at 12 weeks, 14.2 - 114.8 ng / ml at 13 weeks.
  2. the level of protein A, or PAPP-A,
  3. glucose level.

5. What to fear or deviation from the norm

Analyzing the results obtained at both stages of the study, the doctor first calculates the coefficient of deviation of the actual indicator from the required. For this, he divides the first by the average value of the median characteristic of the region of residence of the pregnant woman and her term. The obtained value can often be seen under the abbreviation "MoM", on the basis of which one can judge the presence of any pathologies.

Normally, it should be 0.5 - 2.5, and ideally - 1. At the same time, too low a number (less than 0.5) may indicate a risk of developing Edwards syndrome, and too high (more than 2.5) may indicate a risk of having Down syndrome.

What else can you see in custody? Generalized risk coefficient. In other words, a kind of statistics. For example, an indicator of 1: 500 in relation to Down syndrome indicates that 1 out of 500 pregnant women with the same indicators once had a baby with the indicated disease.

However, it is necessary to judge the results of screening on the basis of two values ​​- a generalized indicator and the level of hormones. For example, they will be considered bad if the first one is in the range of 1: 250 - 1: 380, and the second is less than 0.5 or more than 2.5.

6. Bad results: what to do

First, do not panic. The fact is that the final indicators are influenced by how many weeks the first screening was conducted, or how accurately they determined the duration of pregnancy, as well as some other factors that may show a false pathology.

  • IVF - in this case, the results of hCG will be overestimated,
  • The body weight of a pregnant woman - if it is too large and there is obesity, doctors will see inflated hormone levels, and if it is too small, it will be too low.
  • Diabetes - it will reduce the level of hormones,
  • The psychological state of the future mother - the fear of the first screening can unexpectedly affect its results. The same goes for the last two phenomena.
  • Amniocentesis - procedure for taking amniotic fluid for research,
  • Twins.

If they are excluded, the doctor will refer you for additional diagnostics and tell you when to do it.

More about the first screening can be viewed in this video:

Dear pregnant women! A bad screening result is not a sentence, but a reason for further examination. Remember this, but do not tune in to it in advance. Materialize only good thoughts! Surround yourself with good people and share this article with them in social networks.

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