Ultrasound during pregnancy: transcript. How the size of the fetal egg changes by week

For any expectant mother, it is necessary to be sure that her baby is developing correctly, without various deviations and disorders. Therefore, already after the first ultrasound examination, a pregnant woman learns about such a concept as fetometry of the fetus by weeks. Thanks to this type of ultrasound examination, you can find out the dimensions of the body parts of the fetus, make sure that the doctors set it up correctly and see possible deviations in the dynamics of the child's development.

The main task of fetometry of the fetus

1. After this research method, doctors and the expectant mother will be able to verify the proper level, for example, to clarify the size of the fetus, which is 5 weeks old.

2. Already after 20 weeks, you can clarify the gender of the unborn baby.

3. Thanks to the first ultrasound, you will be able to see the “first smile” of your baby and fix his movement.

Characteristics of the main indicators of diagnosis

Weekly fetometry allows specialists to verify the correct development of the child. The first ultrasound examination has the following indicators:

KTP (coccygeal-parietal size) is typical for short periods of pregnancy, when the fetus has not yet reached a size of 20-60 mm.

BDP (biparietal size) - this indicator is associated with the second trimester of pregnancy and provides an opportunity to find out its term with an accuracy of 10 days.

DB (measuring the length of the thigh) also makes it possible to estimate the gestational age, but the accuracy is somewhat less - up to two weeks. This research option is used when the previous measurement cannot be brought to a satisfactory standard.

Coolant (abdominal circumference) is a characteristic that is already aimed at studying the development of the fetus. After all, now it is possible to visualize a short segment of the umbilical vein, the fetal stomach, the gallbladder and, of course, the venous duct. Therefore, such a concept as fetometry of the fetus by weeks is very relevant in the process of assessing the growth of a baby. At the same time, it is important to follow a small recommendation - such a measurement cannot be carried out when the fetus weighs more than 4 kg.

Second fetometry of the fetus

The subsequent ultrasound examination is typical for the 22nd week of pregnancy. At the same time, you can not only clarify the developmental process of your child, the absence of pathologies and other deviations from the norm, but also find out the gender of the unborn baby.

Now you should carefully pay attention to the following characteristics of phytometry: biparietal size (BDP) and head circumference (OG), abdominal circumference and thigh length (DB). In this case, it is also important to consider the progress in the development of the fetus in general and its parameters. After all, the baby grows in leaps and bounds, and therefore the previous indicators should return to normal. Indeed, the norms of fetometry of the fetus must also be looked at very carefully, further analyzing the overall picture of the development of the child.

Third fetometry of the fetus

In most cases, the third fetometry of the fetus is considered the last for the expectant mother. 33 weeks of pregnancy is the last time for an ultrasound examination. After all, now it is possible to see a fully formed baby, assess his state of health and judge the further method of childbirth. For example, the circumference of the head and abdomen is measured, an assessment is made of the symmetrical development of paired limbs, and a forecast is made of the baby's weight at birth.

Moreover, if there is a need for this, it is possible to conduct such a study as fetometry of the fetus earlier. 32 weeks is considered a sufficient period for this kind of study of a woman in position. If there are no pathologies and striking deviations from the norm, then further ultrasound is not necessary.

Conclusion

In the process of analyzing the information received after an ultrasound examination, you should definitely understand that the baby in the womb does not develop evenly. Since the development itself is characterized by spasmodicity, from this in certain periods it is possible to trace the deviation from the normative indications.

Moreover, special attention should be paid to the genetics of the parents and their physique. So, for example, a pregnant woman who weighs a little and has a short stature will often be the owner of the fetus, which will also deviate from the norm according to the fetometry table in a smaller direction. Whereas a large expectant mother can have a child who also significantly exceeds the standards for weight and general parameters. In this case, do not worry, because this is an individual characteristic of the baby and his mother. And it doesn't affect anything. After all, all people are different.

Only an obstetrician-gynecologist or a specialist in the medical center of genetics is authorized to make a verdict on the results of an ultrasound examination of fetometry. Therefore, the expectant mother must necessarily follow all the recommendations and instructions of doctors, including leading a lifestyle appropriate for a pregnant woman.

After all, only the absence of bad habits (or a complete rejection of them), proper nutrition and compliance with the appropriate daily routine will allow a healthy and active child to be born to the delight of parents. Therefore, you need to immediately think about whether the life and health of your baby is worth your weaknesses? Perhaps a woman should put all the risks aside and change her life for the better. And the child is a reason to do it earlier, at least for his sake.

Throughout the nine months, every mother worries about the correct development of the baby. It is precisely to ensure full control over the development of the child in the womb and the timely detection of any abnormalities that pregnant women are strongly recommended to regularly visit the leading doctor in order to find out the size of the fetus by weeks of pregnancy.

Accurate diagnosis involves the use of ultrasound methods. Based on the results obtained, the specialist can determine how proportionally the baby develops, and whether the data obtained regarding growth and development correspond to the established norms.

What indicators are taken into account?

The key parameters that make it possible to determine the characteristics of the development of the fetus are indicators of its height and weight, but they begin to measure them only in the second part of the first trimester. Until that time, the dimensions of the embryo are so small that their measurement is extremely difficult.

According to medical indications, every pregnant woman is required to undergo at least three ultrasound examinations during all nine months. This number of procedures is considered minimal and can be increased by the decision of specialists, if there is a need to obtain additional information about the development of the fetus.

Periodic ultrasound is necessary for the timely detection of serious pathologies and the prevention of complications. As a rule, such studies are carried out no earlier than 10 and no later than 14 weeks, as well as in the second trimester in the period from 18 to 21 weeks.

To facilitate the task in medical practice, it is customary to measure the size of the fetus by weeks, because the fetal egg increases in volume almost daily.

The results of each ultrasound are recorded in protocols, from which information can be obtained regarding the symmetry of the development of the fetus, its growth rate and the compliance of indicators with established and used standards.

Throughout pregnancy, as the fetus develops, various parameters are taken into account. For example, up to 13 weeks, experts focus more on the analysis of the coccygeal-parietal length, measured from the coccyx to the parietal region of the fetus. This feature of the measurement is due to the fact that the fetus is in a bent position, so the opportunity to obtain the first data on growth appears no earlier than 14 weeks.

During the second scheduled ultrasound, specialists focus more on other indicators presented:

• fronto-occipital size or longitudinal line;
• circles of the skull, abdomen and chest;
• length of the lower and upper limbs.

An important factor indicating the normal development of the fetus is not only compliance with established standards, but also the symmetry of the measurements obtained.

Fetal size by week of pregnancy

The onset of pregnancy occurs by the end of the second week of the menstrual cycle, which is considered the moment of conception. The features of this process are known to everyone since school. Male ejaculation is accompanied by the release of millions of spermatozoa, only one of which, after entering the vagina and through the fallopian tubes, will be able to approach the egg.

During the third week, the formation of an embryonic vesicle occurs, inside which there is a large amount of fluid and cells. This bubble is so small that it is almost impossible to see it without special equipment. To be able to imagine the parameters of the bubble, compare it with a pea, the size of which does not exceed 0.2 mm in diameter.

From the beginning of the fourth week, the active development of the fetus begins, which almost doubles every week. So, by the end of the next week, the length of the fetal egg reaches 0.5 mm. Already at this stage, specialists have the first opportunity to obtain real data on the development of the fetus, which can be presented in the form of a table.

Table 1. Dimensions of the ovum from 1 to 13 weeks

The lengths given in the table are measured from the crown of the head to the coccyx and are averaged. According to experts, due to the distinctive features of development, slight deviations from the given average indicators are allowed. A significant deviation, as well as a violation of the permissible proportions between the indicators, which is an important factor, is a prerequisite for further research.

By the end of the eighth week, the length of the fetal egg reaches 11 mm. According to numerous studies, the weight of the fetus at this stage does not exceed 1.5 grams. Over the next week, there is an increase in weight by another 0.5 g, and by the end of the tenth week, it can reach 4 g.

At the eleventh, through ultrasound, it becomes possible to obtain the first data on the length of the thigh and chest, which are respectively 7 and 20 mm. By this period, the weight of the fetus reaches 11 g. By the end of 12 weeks, the diameter of the chest will reach 24 mm, and the diameter of the thigh - 9 mm.

From the 11th to the 40th week, specialists carefully examine not only the general length indicators, but also the parameters of individual parts of the body, which allows you to get a general and complete picture of the correct development of the fetus.

Starting from the thirteenth, during examinations, measurements of the baby’s skull are also taken into account, whose weight by this time reaches 30 g.

Table 2. Sizes of the fetal egg by week: from the 13th to the 40th

Biparental fetal size by week

Another important indicator that experts take into account in their studies is the biparietal size, represented by the distance between the outer surface of the upper contour and the inner region of the lower contour between the parietal bones.

As in the case of other indicators, minor deviations from the norm are allowed when analyzing the obtained biparietal size. If the established data is exceeded, the specialist must evaluate other parameters, represented by the circumference of the abdomen, the length of the limbs.

The analysis of this indicator is extremely important, because its deviations from the norm in many cases may indicate serious pathologies, represented by hernias, tumors and other volumetric formations, in which the only way out may be termination of pregnancy. The insufficient development of the baby's head or a decrease in its size is also considered undesirable, which may be due to the underdevelopment or absence of the anatomical structures of the brain. In this case, experts also strongly recommend termination of pregnancy.

Often in the third trimester, reduced indicators of BDP are diagnosed, which, if detected in a timely manner, can be successfully corrected.

As a rule, in this case, a diagnosis of intrauterine growth retardation is made, and the pregnant woman is prescribed treatment with drugs that help improve uteroplacental blood flow and ensure the transport of essential nutrients.

In medical practice, the following average indicators of the biparietal size of the fetus are used:

• 8 week - 6 mm;
• 9 week - 8.5;
• 10 week - 11 mm;
• 11 weeks - 15 mm;
• 12 weeks - 20 mm;
• 13 week - 24 mm;
• 14 weeks - 26 mm;
• 15 week - 32 mm;
• 16 weeks - 35 mm;
• 17 week - 39 mm;
• 18 weeks - 42 mm;
• 19 week - 44 mm;
• 20 week - 47 mm;
• 21 weeks - 51 mm;
• 22 weeks - 54 mm;
• 23 weeks - 58 mm;
• 24 weeks - 61 mm;
• 25 week - 64 mm;
• 26 weeks - 67 mm;
• 27 week - 69 mm;
• 28 weeks - 72 mm;
• 29 week - 75 mm;
• 30 week - 78 mm;
• 31 weeks - 80 mm;
• 32 weeks - 82 mm;
• 33 weeks - 84 mm;
• 34 weeks - 86 mm;
• 35 week - 88 mm;
• 36 week - 90 mm;
• 37 week - 91 mm;
• 38 weeks - 92 mm;
• 39 week - 94 mm;
• 40 weeks - 95 mm.

Of course, it is not possible to establish the exact weight of the fetus by means of an ultrasound examination, so experts are guided by other sizes and established norms. For the first time, the weight of the fetus is indicated on the eighth week, from which it becomes possible to obtain the first necessary data.

Table 3. Fetal weight by week

As a rule, from the data obtained after an ultrasound examination, it is not easy for many women to understand how large the fetus is at this stage. To facilitate this task, the size of the fetal egg by week can be compared with well-known objects. As already noted, the first indicators of the length of the fetus can be obtained only in the third week, when its diameter is 0.2 mm. It is extremely difficult to examine the fetus at this time, and it can only be compared with a poppy seed.

By the end of the fourth week, the fruit almost doubles in size and now it can be safely compared with sesame seeds in size. By the end of the fifth, the fetal egg acquires dimensions comparable to sunflower seeds.

Do you know which bird is considered the smallest on the planet? These are hummingbirds, whose sizes rarely exceed 5.7 centimeters, and their weight is in the range from 1.6 to 2 g. It is with the egg of this bird that a human fetus can be compared in size in the sixth week of its development. By the end of the seventh, its size is comparable to the parameters of an ordinary bean.

On the eighth fruit, in terms of parameters, it can be compared with an unripe olive, and by the end of the ninth - with a large grape.

At the tenth week, the fetus reaches the size of a candy, which doctors do not recommend for pregnant women to lean on. The fruit reaches the size of an apricot by the end of the next period, used as a unit of measurement. At the 12th week, the fruit can be compared with a pea pod, and by the end of the thirteenth - with a ripe fig.

Over the next 7 days, the fruit will grow to the size of a medium pear, and after another week - to the size of an avocado. The average weight of newborn kittens is about 100 g. This is how much a human fetus weighs at the 16th week of its development, and in length it can be compared with an average carrot.

At week 17, the fruit can be compared with a medium potato, and at the end of the eighteenth, with a large tomato.

Imagine a big banana in your hands. It is these sizes that the baby reaches by the end of the nineteenth period. At the 20th week, it can be compared to a small hare. Have you seen such an exotic fruit as Thai mango? At 21 weeks, the weight of the fetus can be compared with it.

Among the penguins, the largest and heaviest are representatives of the Imperial species, whose height often reaches 125 cm, and their weight is 50 kg. Eggs of emperor penguins weigh up to 450 g. This is how much a human fetus weighs at 22 weeks of its development.

At week 23, it can be compared in terms of length to a corncob, and by the end of week 24, it can be compared to the weight of a green coconut. By the end of the next period, the size of the baby in the womb can be compared with newborn polar bear cubs, which, despite the impressive volume of adults, are born quite small.

By the end of the 26th week, the baby's weight can be compared with an average head of broccoli, and by the 27th - with a pomelo fruit.

If we take for comparison the length of the baby from the heels to the crown, then at 28 weeks it is comparable to the growth of a newborn tiger cub. The largest bird on the planet is the African ostrich, which can grow up to 200 centimeters and weigh 120 kg. The eggs of these birds weigh an average of 1,200 g. It is this weight that is considered the norm for a baby at the 29th week of its development.

By the end of the next period, the child is comparable to the weight of a six-month-old kitten, and by the end of 31 weeks - to the weight of a newborn lion cub.

In terms of growth, a baby at 32 weeks can be compared with a small blue penguin, and by the end of the next period, it reaches the weight of an average pineapple. At week 34, the baby acquires the size of a ripe melon of medium parameters.

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At various stages of pregnancy, fetometry is regularly performed - this is the determination of the size of the fetus through ultrasound. The data obtained during the survey were subjected to statistical analysis over the years, and on their basis a table was compiled with weekly norm indicators.

It is the main parameter for a more accurate determination of the period and allows you to find out if there are any deviations in the intrauterine development of the baby. Knowing what it is, young parents themselves can, after an ultrasound examination, make sure that everything is in order.

Most often, ultrasound fetometry is performed either with a transvaginal sensor, or traditionally through the abdomen. In the first case, no preparation is required from the woman. A classic ultrasound will show more accurate results if you drink 500 ml of water an hour before the procedure and do not empty your bladder in the early stages. Filled, it will help improve visibility in the uterine cavity. After 12 weeks, this is no longer required, since this function will be performed by amniotic fluid.

The procedure is familiar to everyone: a special gel is applied to the stomach, and everything that happens in utero is displayed on a computer monitor. Modern programs allow you to automatically take measurements of the fetus, and the doctor then compares them with the general table of norms for weeks. This allows you to clarify the gestational age and timely identify pathologies in the development of the fetus.

Why is it called so? The term "fetometry" goes back to the Latin word "fetus" (translated as "offspring") and the Greek "metreo" (meaning "to measure, determine").

Norms and deviations

It is useful for parents to know what the norm is, according to the fetometry table, and when they talk about pathological abnormalities. Seeing a slight discrepancy between the true sizes and official figures, many begin to panic and draw the wrong conclusions, which in most cases turns out to be completely in vain.

• the data of the fetus fully correspond to the sizes in the table;
• they are less than 2 weeks behind or ahead of them (this period is acceptable for individual characteristics);
• the indicators are not on the same line, but scattered, but this difference is no more than 1 line: these discrepancies are acceptable due to the spasmodic intrauterine development of the fetus.

Everything else is considered a deviation. It is especially dangerous when the fetometry of the fetus once again shows that the same size is more or less than the norm by 2 or even more lines.

For example, a growing head circumference may indicate, but to confirm the diagnosis, additional data obtained during dopplerometry and CTG, and monitoring in dynamics will be needed.

For comparison. If all dimensions of the fetus "fit" into the norm indicated in the fetometry table, except, for example, the length of the thigh, this is not at all an indicator of pathology. Perhaps the parents or other relatives of the child are simply the owners of very long (or, conversely, too short) legs.

In the presence of deviations, such serious diagnoses as "", "" are confirmed by two doctors: not only an obstetrician-gynecologist, but also a medical geneticist. They assess the genetic predisposition of the fetus and determine the causes of the identified pathology (chromosomal abnormalities, bad habits, parental age, intrauterine infection, etc.).

It is very important that the obstetrician-gynecologist is primarily involved in deciphering the obtained indicators: the ultrasound specialist only provides him with a summary sheet, which indicates what sizes and how much they differ from the norm of fetometry for a given gestational age. What parameters are taken into account during screenings?

Description of key indicators

To figure out what weekly fetal fetometry data are contained in the tables, you need to know the symbols for these parameters and their interpretation.

• BDP - biparietal size, the distance between the parietal bones, describes the development of the nervous system.
• DB - thigh length.
• DG - leg length.
• DN - the length of the nasal bone.
• DP - shoulder length.
• KTR - coccyx-parietal size.
• LZR - fronto-occipital size.
• OG - head circumference.
• OG (DHA) - chest volume (diameter of the chest).
• OC - ​​abdominal circumference.
• PJ - transverse diameter of the abdomen.
• PYa - a fetal egg where the child develops.
• SJ - sagittal diameter of the abdomen (measured in the anterior-posterior direction).
• TVP - the thickness of the collar space.

This is the interpretation of the indicators that are most often indicated in the fetometry table. It may also include the lengths of other bones - more - and fibula, ulna, radius, as well as the foot. But they no longer have such significance for the detection of pathologies - they are used for comparison only as additional information.

Among other things, you can calculate the weight of the fetus by fetometry, carried out after the 20th week of pregnancy. All calculations are made automatically by the ultrasound machine itself based on the term, BPR, LZR, OZH, DB and OG. They give very accurate results and allow you to compare them according to the table with the norms.

I trimester

The first fetometry is prescribed at 12-13 weeks. Its purpose is to identify fetal malformations in early pregnancy.

This ultrasound screening does not identify a specific disease, but only points to markers that are typical for it. Based on the results obtained, additional studies may be prescribed. All suspicions that have arisen are confirmed or refuted by invasive laboratory techniques.

Some indicators of fetometry can be specified. For example, during the first screening, specialists use a table of average CTE values, since this size is very important for identifying abnormalities in the intrauterine development of the fetus.

Doctors include an increase in CTE by 1-2 weeks to the variants of the norm. If the pregnancy is not complicated by the Rh conflict, this may mean that the baby will be born a real hero and its weight will be more than 4 kg, and in some cases this may be an indication for carrying out.

These are the important data that the first fetometry gives into the hands of specialists.

About the timing. The first ultrasound screening is carried out during this period because of the TBP indicator. Until 11 weeks, it is so small that it cannot be measured. And after 14 weeks, this space is filled with lymph, which distorts the results of the study. It is this parameter that is a marker for most fetal chromosomal abnormalities.

II trimester

The time frame for the second ultrasound fetometry should be within the following timeframes:

• not earlier than 16 weeks;
• no later than 20;
• the best option is week 17, which, if abnormalities are detected, will allow more accurate additional genetic examinations;
• sometimes ultrasound is also performed at 21-22 weeks, but these are already the most extreme and undesirable dates.

The first ultrasound screening gives the most accurate results, but often even they are not enough to make a diagnosis. To do this, many indicators need to be seen in dynamics. Here it is just the data of the second fetometry that demonstrate it.

It performs the following tasks:

• identify defects that cannot be determined in the first trimester;
• confirm / refute the diagnosis previously made based on the results of the first screening;
• determine the risk level of suspects;
• detect deviations in the formation of a small organism.

Fetometry II trimester is assigned only to those women who, according to the results of the first ultrasound, were at risk.

Approximate norms of ultrasound at this stage of pregnancy are presented in the following tables.

Height Weight

Abdominal circumference

Head circumference

Calf length

Thigh length

Humerus length

Forearm bone length

If for some reason the timing of the second fetometry was shifted, you can use a table with averages from 21 to 27 weeks:

After examining the data of the second fetometry, the gynecologist can refer the woman for a consultation with a geneticist or independently prescribe invasive techniques to diagnose suspected pathologies. In cases where the diagnosis is still confirmed, a decision is made about the future of the pregnancy.

If therapeutic adjustment is not possible, artificial induction of labor is performed (for artificial labor, read in). If the detected pathology is reversible, treatment is prescribed as soon as possible in order to save the baby.

III trimester

The third fetometry can be prescribed on any day of the III trimester of pregnancy. The optimal period is 32-33 weeks. Since at this stage the matter is approaching childbirth, ultrasound is carried out more carefully than before.

For example, the baby's face is already perfectly visible, which makes it possible to identify such pathologies as the cleft palate or cleft lip. The doctor finds out how developed the fetus is in accordance with the gestational age.

It is usually not recommended to conduct such studies after 34 weeks. However, there are times when they are appointed immediately before the birth itself (at 37-38 weeks) in order to make the final decision on a caesarean section or.

Table of average values ​​of the third fetometry of the fetus by week

If there are deviations at this stage, the woman is offered hospitalization. With the negative dynamics of the testimony received, doctors may decide to stimulate preterm labor.

Useful information. Everyone around (women, and often doctors themselves) like to talk about the importance of the first two fetometry and the optionality of the third. But after all, only she allows you to make the right decision on how to carry out the upcoming birth with minimal losses for mom and baby.

Information from the tables of fetometry of the fetus is for informational purposes only. It is not recommended for parents to draw any independent conclusions by comparing the results obtained with the norms, because they do not always reflect reality and require mandatory interpretation by specialists.

From the moment of registration, the health of the woman and the fetus is closely monitored by obstetrician-gynecologists. Throughout the entire gestation period, the pregnant woman undergoes routine examinations. Some of the problems found can be solved therapeutically or surgically, others require termination of the pregnancy. One of the mandatory diagnostic methods that allows you to find out the parameters of fetal development is fetometry. How is fetometry done and what indicators are considered the norm?

What is fetometry and what is its purpose?

To have an idea about the development of the child (normally it passes or there are deviations), doctors need to constantly monitor the performance of the fetus. One of the planned examinations, which is prescribed to all women, regardless of the individual characteristics of the course of gestation, is fetometry.

What does fetometry include? This is the definition of the size of the fetus - height and weight. In ultrasound diagnostics, the following indicators are considered key (their abbreviation in Russian and English and decoding):

• MP, FW - mass;
• KTP, CRL - coccyx-parietal size;
• BDP, BPD – biparietal head size of the embryo;
• DB, FL - size of the femur;
• OC, AC - abdominal circumference;
• OG, NS - head circumference;
• LZR, OFD - fronto-occipital size.

Fetometry is performed using ultrasound. A pregnant woman undergoes sonography according to the plan in each trimester - at 11-14 (most often 12th) weeks, 18-21 weeks and at 32-33 weeks. As a rule, sonography is performed in the usual way through the abdominal cavity or transvaginally. Special preparation for the study is not required, only in the first trimester before a transabdominal examination, a woman needs to drink 1 liter of water 1 hour before visiting the office so that the bladder is full.

Only by fetometry it is impossible to draw conclusions about the correct development of the fetus. The parameters of the child will largely depend on his genetic and individual characteristics. If the mother and father are large, then the baby will be ahead of their peers in development. In case of growth retardation, a second ultrasound scan is prescribed after 2 weeks, often the baby manages to catch up by this time.

What is evaluated at the first ultrasound?

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The first screening ultrasound is sent shortly after the woman is registered. The optimal date for ultrasound diagnostics is 11–12 weeks, but if a pregnant woman went to the antenatal clinic later, she can be sent for sonography right away. Why is the screening examination scheduled for these periods? One of the most significant indicators in the early stages of gestation is the thickness of the nuchal space of the embryo. Previously, this parameter is indistinguishable, and after the 14th week it is filled with lymph, which distorts the readings.

Normal performance

At the first ultrasound, the doctor measures the heart rate of the fetus, looks at the presence of vital organs. Also pay close attention to the following parameters:

• TVP - the area between the soft tissues that cover the spine and the inner surface of the skin. Allows you to detect chromosomal abnormalities, such as Down syndrome.
• KTP - coccygeal-parietal size. It calculates the size of the fetus and the gestational age.

The table contains the norms of the results of ultrasound in the 1st trimester:

What does an embryo look like compared to a fruit? Until the first month, it resembles a poppy seed in size. By the end of the second month, it corresponds to a large grape of 5 cm. During the first fetometric study, it is comparable to a ripe fig of 7 cm.

What is considered abnormal and why?

To determine the norm and deviations in medical practice, the concept of percentiles is used. Among a large sample, the average value is determined - it is called the 50th percentile. The norm of ultrasound is in the range of 5-95 percentiles, and everything that goes beyond these limits is regarded as a deviation.

Non-compliance with normal values ​​indicates the possibility of intrauterine diseases and developmental anomalies:

• Increased TVP often indicates the presence of genetic pathologies, which include Down's syndrome. Its probability is indicated by a high TPT rate, which stands for the thickness of the prenasal tissue. If a discrepancy is found, the woman is sent for additional examinations - analysis for alpha-fetoprotein, hCG, amniocentesis, placentocentesis, cordocentesis.
• Irregular heart rhythm may be due to congenital heart disease or hypoxia. Tachycardia and bradycardia can indicate oxygen starvation.
• A high KTR, which is 1–2 weeks ahead of the values, is considered the norm by doctors. Most often, this indicates that the child will be large. If the mother has diabetes mellitus or the likelihood of developing an Rhesus conflict is increased, then additional examinations are required.
• If deviations in the fetal anatomy are detected (incorrect anatomy of the bones of the cranial vault, spine, stomach, heart, limbs, abdominal wall), the sonologist enters them in a special column. Together with an obstetrician-gynecologist and, if required, geneticists, a conclusion is made on the advisability of prolonging gestation.

What indicators are studied in the second trimester?

Previously, ultrasound diagnostics in the second trimester was performed at the 25th week of pregnancy, but now it is performed at the 4th month of gestation. This is due to the need to detect malformations at an earlier stage. In addition to the parameters of the fetus during this period, they study the children's place, its size and degree of maturity.

Standard sizes

In the second trimester of pregnancy, you can better consider the size of the baby and specific organs. During this period, more attention is paid to the following indicators of ultrasound:

• baby weight;
• growth;
• abdominal circumference;
• fronto-occipital size;
• biparietal head size;
• leg size;
• thigh length;
• humerus size;
• forearm bone length.

The table shows the results of fetometry in the 2nd trimester in accordance with the protocol:

Week of gestation	Weight, g	Length cm	coolant, mm	OG, mm	LZR, mm	BPR, mm	DG, mm	dB, mm	DP, mm	DKP, mm
16 week	100	11,6	88–116	112–136	41–49	31–37	15–21	17–23	15–21	12–18
17 week	140	13	93–131	121–149	46–54	34–45	17–25	20–28	17–25	15–21
18 week	190	14,2	104–144	131–161	49–59	37–47	20–28	23–31	20–28	17–23
19 week	240	15,3	114–154	142–174	53–63	41–49	23–31	26–34	23–31	20–26
20 week	300	16,4	124–164	154–186	56–68	43–43	26–34	29–37	26–34	22–29

On the second screening study, it is already possible to estimate the size of the placenta. At week 20, it fluctuates between 1.67–2.86 cm. Amniotic fluid index by week:

• 16 – 74–202;
• 17 – 78–212;
• 18 – 81–221;
• 19 – 84–226;
• 20 – 87–231.

What are deviations from the standard?

The advanced maturation of the placenta is most often observed in smoking mothers. In addition, this indicator is affected by the presence of diabetes mellitus, the development of preeclampsia, the appearance of intrauterine infections.

Polyhydramnios indicates malformations in the development of the child, Rhesus conflict. Oligohydramnios indicates severe abnormalities in intrauterine development, pathologies or the absence of kidneys in the fetus.

Visualization can be difficult due to the high content of subcutaneous fat. In this case, the doctor indicates in the protocol the cause of the difficulty - PZHK.

The second screening ultrasound allows you to detect pathologies of fetal development that were not visible at the first examination:

• developmental delay, if the indicators are symmetrically below the specified norm;
• asymmetric reduction of the femur, humerus, tibia and forearm indicate skeletal dysplasia;
• an increase in the skull indicates hydrocephalus;
• by measuring the face, one can judge the presence of such pathologies as cyclopia, anophthalmia, cleft lip and palate;
• scanning the spine helps to detect its splitting;
• the absence, underdevelopment or abnormal structure of the internal organs indicate intrauterine anomalies that are incompatible with life.

Fetometry parameters of the fetus in the third trimester

The third fetal ultrasound is prescribed for 32–33 weeks of gestation, although, according to individual indications, the period can be shifted by several weeks. During this period, the baby is already fully formed, and it becomes possible to assess malformations that were not visible before. Particular attention is paid to the placenta and amniotic fluid, as well as fetal presentation.

Table of sizes of the fetus, body parts and organs are normal

The final fetometry is important, because it is according to its results that doctors choose the method of conducting the birth process. In the final trimester, the average data on the size of the baby and its weight are also evaluated.

The table shows the average fetometry in the third trimester:

On ultrasound, the obstetrician-gynecologist looks at the presentation of the fetus, the tactics of delivery depends on this:

• direct head presentation - natural delivery;
• oblique, transverse or direct pelvic presentation - caesarean section (as a rule).

Possible deviations and their interpretation

Deviations from normal indicators allow predicting possible complications during the birth process and detecting congenital malformations. Interpretation of deviations:

• Weight and height are more than normal. A large baby will complicate the delivery process. This may be an indication for surgical intervention, otherwise the woman in labor will rupture when the child passes through the birth canal.
• Low location of the placenta. In such a situation, natural childbirth is acceptable, but the risk of bleeding is high.
• In the third trimester, anomalies that did not appear before become visible. On the last examination, you can find a cleft lip, a cleft palate, an aneurysm of the vein of Galen.
• Indicators below the norm allow diagnosing developmental delay syndrome. This diagnosis allows you to take timely measures to maintain the life of the baby.

Rules for decoding the result of an ultrasound specialist

The interpretation of ultrasound during pregnancy is performed only by a sonologist, and the diagnosis is made by an obstetrician-gynecologist, who is based on the indicators of ultrasound diagnostics and other methods. Calculation of indicators is based on obstetric weeks, which are counted from the date of the last menstruation. In fact, the fetus is 1.5–2 weeks younger, but in order to avoid errors in calculations, gynecologists use a reference system from the first day of menstruation.

One of the main rules that specialists follow when deciphering ultrasound is not to make a diagnosis based on the results of sonography alone. If an abnormal course of gestation is suspected, the pregnant woman is prescribed a second examination and sent for additional diagnostics.

Despite the fact that specific numbers are indicated in the ultrasound report - limb length, volume, height and weight, you should not try to interpret them yourself. The limits of the norm indicators are large, borderline data do not necessarily indicate deviations, and the expectant mother needs to protect herself from stress.

Deviations during pregnancy or in the development of the child can be determined by the results of periodic examinations by a gynecologist and control studies using sonography (ultrasound). The fruit is constantly growing. Its size is increasing every week.

Causes of fetal size differences

The size of the fetus by week of pregnancy is constantly changing: they differ even when measured with a time interval of several days. It's connected with:

• rapid growth and differentiation of tissues;
• genetic factors: in large parents, the fetus will also be relatively large;
• mother's diet: she can overfeed the unborn child and significantly complicate the process of childbirth.

Therefore, conditional norms have been defined, which doctors are guided by in order to assess the size of the fetus by weeks of pregnancy. The parameters obtained may differ slightly from the calculated figures, since each case is individual.

Required Research

According to the established norms, during pregnancy, each woman must undergo 3 ultrasound procedures - the amount calculated for a normal pregnancy. If necessary, the specialist prescribes additional procedures. These studies are required for the timely determination of fetal pathology and the prevention of serious complications.

Fetal size must be measured week by week due to its rapid growth. The results can be assessed:

• its symmetry;
• rates of growth;
• compliance of the obtained indicators with the established standards.

Measurements in the first trimester

In the first trimester (approximately 12 weeks) the process of embryogenesis lasts: the formation and development of the embryo takes place. From the 12th week, the embryo is called a fetus - all organs and systems, the structure of the skeleton is fully consistent with a person, the limbs are lengthened, the blood type is established. The size at this stage is 7 cm.

Second trimester indicators

The second trimester is 18-21 weeks. At this time, the following mandatory dimensions are determined:

• BPR - biparietal - between the contours of the parietal bones (outer upper and inner lower);
• LZR - fronto-occipital.

Deviations in biparietal dimensions require the evaluation of additional measurements:

• abdominal circumference;
• limb length.

If a significant deviation of this size is detected, the presence of various volumetric formations is revealed, which most often include:

• hernia of the brain;
• dropsy;
• tumors.

When conducting a study, underdevelopment of the head is often found, which manifests itself in a decrease in its size and insufficient physical development.

This indicates the absence of brain structures. In all these cases, termination of pregnancy is indicated, since the fetus is not viable.

Third trimester options

In the third trimester, a decrease in BDP is often found. At these times, the pathology is successfully corrected: therapy is prescribed to improve uteroplacental circulation. In such cases, a diagnosis of intrauterine developmental disorders is made.

Table of fetal sizes by week of pregnancy by ultrasound:

As mentioned, in addition to the compliance of all sizes with the established norm, the symmetry of the measurements obtained is important. These figures are average. Some deviation of measurements in one direction or another is acceptable. In case of significant deviations or violations of proportions, further studies are prescribed.

Important milestones for fetal development at different stages of pregnancy

From 11 to 40 weeks, not only the length, but also the dimensions of certain parts of the body are examined. On their basis, conclusions are drawn about the correct development of the fetus as a whole.

Week 12 is the last of. At this time, it is necessary to conduct the first ultrasound, which is included in the pregnancy monitoring plan. Organs are already formed. The circulatory and urinary systems are fully developed. The intestines are already able to contract and remove digested food. There is a simultaneous excretion of waste products of the mother and fetus. Fetal weight - 15 g, KTR - 7-9 cm.

KTP or coccygeal-parietal size of the fetus is its greatest length without taking into account the limbs and the yolk sac. That is, this is the distance from the crown of the head to the coccyx.

Week 13 - the beginning of the second trimester of pregnancy. Fetal weight - 20 g, KTR - 8-10 cm. Growth and further development of systems and all organs continues. The laying of the skeleton begins, soft bones appear, in the future they become stronger and harder. At this time, it is especially important for the mother and the unborn child to consume calcium in large quantities. The intestines develop - villi form on its walls for better digestion of food.

14 weeks pregnant:

• the face changes - it acquires the outlines of a human and facial expressions begin to appear;
• prenatal fluff grows on the body (lanugo);
• hormones are produced;
• the development of the reproductive system continues: in a girl, the ovaries descend into the lower abdomen, in boys, the prostate develops;
• the lungs function - the fetus can draw amniotic fluid in and push it out.

Weight - 30 g, KTR - 8-15 cm.

15th week of pregnancy - during this period, the fetus already resembles a newborn baby, but small in size. At this stage:

• the intestines are functioning - the first feces (meconium) appear;
• the gallbladder begins to shrink;
• the placenta is enlarged.

Weight - 50 g, average CTE - 10 cm.

17 week:

• bone formation continues;
• a rumor appears: the child begins to hear an appeal to him, recognizes the voices of his parents;
• pushing in response to loud noises.

Weight - 150 g, average CTE - 18 cm.

18 week:

• a completely solid skeleton has formed, as well as fingers on the hands;
• the appearance is laid down: it is already clear what kind of hair the child will have - their color;
• a pattern has formed on the fingertips;
• the gender of the child is determined;
• the functioning brain continues its development: new convolutions appear.

Weight - 200 g, average CTE - 20 cm.

19 week:

• photosensitivity appears: the unborn child begins to distinguish light, turns his head towards it;
• adipose tissue develops (after the birth of a child, it disappears in 3 days);
• teeth begin to form, so a woman should actively take calcium.

Weight - 230 g, average CTE - 22 cm.

20-22 weeks - the second scheduled ultrasound is scheduled:

• formed face,
• hair appeared on the head;
• the skin is finally formed - it becomes four-layered;
• the sebaceous glands begin to function: they produce a white secret, which is stored on the skin due to the gun (lanugo) on it and protects it from further exposure to amniotic fluid.

From the 20th week, heart sounds are heard with a stethoscope.

Weight - 300 g, average CTE - 25 cm.

At week 21, the development of the fetus slows down, the growth rates that were fast before this decrease: a systematic weight gain and adipose tissue begins.

Weight - 360 g, average CTE - 27 cm.

22 week:

• the proportions of the body gradually normalize: the head and abdomen become approximately the same size - 5 cm;
• reflexes progress in development: movements become more accurate;
• further development of internal organs continues.

Weight - 475 g, average CTE - 28 cm.

Week 23: the development of the child continues: Weight - 500 g, average CTE - 30 cm.

Changes occur in a pregnant woman:

• Braxton-Hicks contractions may occur - these are short-term chaotic contractions of the uterus; not everyone feels them;
• increased production of melanin leads to the appearance of a vertical dark strip on the abdomen, darkening of the nipples, and the appearance of age spots on the skin.

All new signs that have appeared associated with increased melanin synthesis are temporary, in the postpartum period they will gradually disappear.

Week 24: active growth and development of the fetus continues: due to the increase in size, almost the entire uterine cavity is occupied by it, due to the lack of space in it, the classic position of the embryo occurs.

Weight - 600 g, average CTE - 33 cm.

25 week:

• further formation of the spine and strengthening of muscles;
• the brain functions well enough: the child meaningfully pushes, expressing emotions.

Weight - 700 g, average CTE - 35 cm.

26 week:

• the eyes are finally formed;
• the structural structure of the tongue has fully developed: thanks to the papillae that have appeared on its surface, bitter and sweet tastes are felt;
• makes active movements.

Weight - 800 g, average CTE - 36 cm.

27 week:

• a large stage of weight gain begins in the mother and in the fetus - from this period it is necessary to control the mother's nutrition and limit the intake of carbohydrates;
• the pituitary gland of the fetus begins to synthesize growth hormone - somatotropin, in connection with this, an increase in the size of the body and limbs accelerates;
• the skin is still very wrinkled from soaking in the liquid, but less red.

Weight - 900 g, average CTE - 36 cm.

Week 28: all the senses function in the child: he begins to see, hear, taste, can touch - from this period you can talk to him, turn on calm music, he reacts with his movements.

Weight - 1000 g, average CTE - 36 - 37 cm.

29 weeks: the period when the fetus takes head presentation. If this does not happen, there are still a few weeks left for him to move into the correct position. In case of further breech presentation, a caesarean section will be performed.

Weight - 1250 g, KTR - 37 cm.

30 weeks is maternity leave. The fetus continues to develop vision, develop the nervous system;

Weight - 1400 g, average CTE - 37 cm.

From 30 to 32 weeks - the next mandatory ultrasound.

Weight - 1600 g, KTP - 40 cm.

32 weeks. Bones are strengthened. At this stage, it is necessary to interrupt the intake of calcium - an excessive amount of it can lead to infection of the fontanel.

Weight - 1800 g, average CTE - 42 cm.

33 week:

• a supercraftant appears in the lungs, thanks to which they will be dealt with at birth;
• further development of all organs continues, preparation for birth.

Weight - 2000 g, average CTE - 43 cm.

34 week:

• all systems and organs of the fetus are almost completely formed;
• there is an active weight gain, at the same time the weight of the mother increases;
• due to the large size of the unborn child and insufficient space in the uterus, pressure on all organs of the mother increases: during this period, the mother may have problems with digestion in the form of heartburn, belching.

Weight - more than 2000 g, average CTE - 43 cm.

35 week. Due to the limited space in the uterus due to the continued growth of the fetus, there is a decrease in its motor activity - this is a normal phenomenon. Only in the case of a complete absence of movement, you should immediately consult a doctor.

Weight - more than 2500 g, average CTE - 46 cm.

In the remaining periods of pregnancy, the development of the fetus is completely completed, there is an increase in growth, weight is gained according to the tables. At 38-42 weeks, childbirth occurs.