How much does a baby weigh in the belly? How to calculate the weight of a baby in the womb

Expectant mothers are always very interested in what weight their baby will be born with. Therefore, they are keenly interested in how much the baby weighs while still in the womb. This question is also important for doctors. Although the weight of the fetus is called estimated, even it allows you to learn a lot about the development of the baby. What is the usual weight of a baby in the mother’s womb during different periods of pregnancy and what does it depend on, we will tell you in this material.

How is the baby growing?

At the very beginning of pregnancy, all babies, regardless of gender, race, heredity, grow exactly the same, adding millimeters and grams to their tiny weight weekly. All embryos grow at approximately the same speed, and only then, when the individual characteristics of the little person begin to appear, differences begin to appear.

It is possible to measure fetal growth even with the most modern ultrasound machine. only in the second half of the first trimester. Up to 8 weeks, only the diameter of the fetal egg is measured, and this criterion is considered the main one, indicating the growth of the embryo.

The dimensions of the baby itself are not yet available for measurements, the only exception being the coccygeal-parietal size, but it does not provide grounds for calculating the weight of the embryo.

You can talk about the weight of the fetus for the first time when undergoing an ultrasound examination, starting from the 11th week. It is at this time that the first differences between babies begin to appear - some babies are larger, others are smaller. At 7-8 weeks the baby weighs about 3 grams, but this is so small that the weight has no diagnostic value.

After 12 weeks, the baby begins to actively gain weight, sometimes doubling its weight in just one week. At this time, all organs and systems, as a rule, are formed, and a period of intensive growth and improvement begins. Gradually, the baby begins to store subcutaneous fat, hence the rapid weight gain. The biggest increase awaits the baby in the third trimester.

In recent months, the child is already ready to be born physiologically, all that remains is to “get better”, all organs and systems are working. Since a fairly grown baby can no longer actively move in the uterine cavity, his main occupation becomes sleep and occasional gentle movements in the now cramped uterus. Over the past two months, the baby gains the weight it will have at birth, and only in the last days before birth does the weight gain almost stop.

From the end of the second trimester, female fetuses gain slightly less than male children. Therefore, in the third trimester they are almost always distinguished by more miniature forms, although this is not a 100% rule - there are girls who, in terms of weight, can leave any boy behind.

What affects weight?

The weight of the fetus is primarily influenced by heredity. If mom and dad are big and large, then the probability that they will have the same “hero” is more than 90%. Miniature, short, thin mom and dad usually give birth to a baby with low weight. It is quite difficult for any external factors to influence this pattern.

However, pregnant women should remember that there are factors that cannot but affect the baby’s body weight. First of all, it's nutrition. If a mother eats well and in a balanced manner, then her baby, along with the blood, will receive a balanced set of nutrients that will help him develop and grow harmoniously. If the expectant mother overeats, is addicted to carbohydrates, cakes, pastries, and abuses vitamin complexes, even if she does not have a vitamin deficiency, then the child receives all this through the uteroplacental bloodstream. The mother's weight is growing, and the baby's weight is also growing.

If the mother’s nutrition is insufficient, poor in vitamins and minerals, proteins and carbohydrates, then the child, willy-nilly, experiences a shortage of the substances he needs so much, his body weight will be less than it could be, taking into account genetic characteristics.

Smoking during pregnancy can also affect the weight of the fetus. 70% of pregnant women who smoke give birth to underweight children. In the same way, alcohol, drugs, and even conventional medications that the mother took during pregnancy affect the fetus. The mother’s nervous stress and worries, hard physical work, and working conditions in hazardous work have an adverse effect on the baby’s body weight.

Some chronic diseases that the expectant mother has also affect the baby’s weight. For example, with diabetes mellitus or gestational diabetes, which first appeared during pregnancy, there is a chance of giving birth to a large or even gigantic baby, whose weight will exceed 5 kilograms. And insufficient fetal weight can manifest itself in chronic diseases of the kidneys, liver and heart in a woman.

Features of the course of pregnancy cannot but affect the weight of the child. If everything is going smoothly, then there is nothing to worry about. But a baby who develops in conditions close to extreme - against the background of the threat of miscarriage, with other complications of pregnancy - is unlikely to be a hero.

If the pregnancy is multiple, a woman is carrying two or three babies, then the weight of each will be less than normal, and this is quite natural.

How is it determined?

Obstetricians-gynecologists use several formulas to calculate the estimated weight of the fetus. If you want to try to calculate how much the baby weighs, the mother can do it herself.

Lankowitz formula

Experts consider this method of calculation to be the most accurate, although, unfortunately, it cannot be done without errors. To make the calculations, a woman will need to look at her exchange card on the page of her last visit to the doctor. There she will find two important parameters for calculation - her abdominal circumference (AC) and the height of the uterine fundus (VSDM or VDM).

Both of these values ​​are added, after which the mother’s mass in kilograms and her height in centimeters are added to the resulting sum. The resulting number is multiplied by 10. For example: gestational age is 30 weeks, abdominal circumference is 110, fundus height is 30. The pregnant woman’s height is 170 cm, weight is 70 kilograms. (30+110+170+70) x10=3800. The error in this calculation can be up to 0.5 kg. Therefore, it is reasonable to assume that the woman has a large baby - its actual weight at this stage already exceeds 3 kilograms.

Bublichenko formula

To calculate, you only need to know the body weight of the expectant mother at the current moment. Her weight is divided by 200, the resulting number is multiplied by 10. For example, a woman’s weight is 80 kilograms. (80/200) x10= 4. The error in this method is large, it fluctuates within a kilogram, which is why obstetricians have been trying not to use this formula lately

Yakubova's formula

For these calculations, a woman who has decided to practice arithmetic and satisfy her maternal curiosity will need data on the height of the fundus of the uterus and the circumference of her abdomen. You can find them in the exchange card; this data is entered into it at each scheduled appointment. The VMR is added to the abdominal circumference, and the resulting amount is divided by 4 and multiplied by 100. For example, the VMR is 30, the abdominal circumference is 100. (30+100) / 4 = 32.5. When multiplied by 100, the result is 3250 g.

Jordania formula

To calculate, you will again need to know the height of the uterine fundus and the abdominal circumference of the expectant mother. These values ​​are multiplied by each other. For example, GMD -30, circumference - 100, it turns out that the expected weight of the child is 3 kilograms.

Ultrasound

The most accurate calculations are those made using the sonographic method, that is, ultrasound. To derive the estimated body weight of a child, special equations are used that are compiled by the software of the scanning machine; the Hadlock method is most often used.

As the necessary mathematical values ​​for the equations, the dimensions that the somnologist determines on ultrasound are used. This biparental size of the baby's head, length of the femur, circumference of the tummy and head.

To make it clearer, we present these equations using the two most popular calculation methods (according to Hadlock and Shepard):

• Shepard – Log10 BW = -1.7492 + 0.166 (biparental size) + 0.046 (fetal abdominal circumference) – (2.646 [ (abdominal circumference) X (biparental size) ] / 100).
• According to Hadlock – Log10 BW = 1.3598 + 0.051 (Child’s abdominal circumference) + 0.1844 (femur length) – 0.0037 (abdominal circumference X femur length), or Log10 BW = 1.4787 + 0.001837 (biparental size head) 2 + 0.0458 (abdominal circumference) + 0.158 (femur length) – 0.003343 (abdominal circumference times the length of the femur).

Thus, the measured parameters of the baby become components of a mathematical expression, as a result of which the computer produces a result. It is usually indicated in the ultrasound diagnostic protocol in the section “Estimated fetal weight”. The margin of error for singleton pregnancies ranges from 8 to 10%, when carrying twins, the error increases to 15%.

This method cannot be called accurate, like in a pharmacy, but medicine has not yet invented anything more accurate.

It is on the basis of ultrasound data that all currently existing norms for fetal weight by week and month of pregnancy have been created.

Norms at different times

It is difficult to say for sure what the body weight of a child who has not yet been born should be, because we are all different - tall, short, thin and plump. Babies in the womb also have individual characteristics. Therefore, there may be a spread, but average values ​​still exist.

Starting from the 11th week of pregnancy, ultrasound machines can already calculate the first weight indicators:

This table is compiled without taking into account the gender of the child. Some specialists who want to achieve the greatest accuracy in situations where the method of delivery and other important issues depend on the expected weight use tables developed by doctors from Germany to measure the weight of children of European appearance in the early 90s of the last century. It is compiled taking into account the gender of the fetus.

Table of normal values ​​for the expected weight of babies of different sexes:

It is no coincidence that the German tables, which are used all over the world, begin at 23 weeks of pregnancy. It is at this time that children of different sexes begin to develop bodies according to gender characteristics, which is why weight gain in boys and girls begins to differ from each other. At earlier stages, this difference between babies of different sexes is not present, or it is not expressed clearly enough and remains unnoticed for diagnosis.

Deviations from normal values

It is considered normal if a child is born at 39-40 weeks with a weight from 3000 to 3800 g. However, those babies who are born weighing up to 3 kilograms, and those who weigh more than 4.5 kg at birth, have neonatologists are not concerned.

Obstetricians urge expectant mothers not to panic about the difference in the numbers presented in the reference tables and their real numbers.

Firstly, you should always make an allowance for error (plus or minus 500 g at a minimum), and secondly, babies grow in leaps and bounds, so at 34 weeks the baby can upset the mother by lagging behind the average statistical norms, and by 36 weeks reach normal average value or even approach the upper limit of normal.

If the baby persistently exceeds the norm throughout all ultrasound examinations during pregnancy, they speak of a large fetus. The trend towards a larger baby can be noticed already in the second trimester. Such a conclusion cannot be made based on ultrasound alone. several studies are required over several weeks.

At the same time, attention is also paid to instrumental measurements - the circumference of the expectant mother’s abdomen and the height of the uterus. With a large fetus, the GMD usually exceeds the norm (at 32 weeks, when the norm is 32 cm, for example, this parameter is increased to 34 cm, and at 36 weeks, instead of the required 36 cm, it is about 39 centimeters).

If the baby in the mother’s womb noticeably lags behind the average values ​​and, over the course of several diagnostic measurements, “passes” only at the lowest limit of the norm (5th percentile), then doctors prescribe an additional examination, the purpose of which is to identify the consistency of the uteroplacental blood flow, possible pathologies of the fetus, including hereditary and chromosomal, intrauterine growth retardation, the presence or absence of intrauterine infections, Rh conflict.

To do this, they perform expert-class ultrasound, ultrasonography, do tests for infections, and perform clinical blood and urine tests. If necessary, the woman is sent for a consultation with a geneticist and undergoes invasive diagnostics. A woman with suspected fetal malnutrition is prescribed regular monitoring of the baby’s condition using cardiotography (CTG), and additional treatment is prescribed (sometimes in a hospital), which includes taking vitamins and medications to improve uteroplacental blood flow. The estimated weight of the baby is monitored using intermediate ultrasound examinations.

Lagging behind the norms is not considered particularly dangerous if all the baby’s parameters are reduced symmetrically. Then this may be a variant of the norm, an anatomical feature of this child.

Starting from 7 months of pregnancy, the baby’s weight is not only a subject of burning curiosity for expectant mothers, but also important information for obstetricians. Based on general data about pregnancy and the approximate weight of the baby, they draw conclusions about the best way to bring the child into the world.

Reliability of determination and errors

As mentioned above, the most accurate method for determining the expected weight of the baby in the mother’s womb using ultrasound is considered. According to data received by American doctors from Florida, the error in the Hadlock calculation was approximately 14% of the baby’s body weight. In other words, the real mass differed from that predicted by the apparatus by 14% in one direction or another. This is the highest result to date.

The methods that obstetricians used before the widespread use of ultrasound, formulas and measurements are practically not used today, because there is no need for them. To obtain information about the possible body weight of the baby, you do not need to calculate anything. A computer program will help you calculate everything. The accuracy of the formulas (presented above and some others) is estimated at approximately 40-55%. Whereas with ultrasound, the accuracy of assessing a child’s body weight is almost 82%.

The most accurate method, as gynecologists like to say, is weighing. Therefore, those who want to find out how much the child weighs in grams just need to be patient and wait for the birth. They will answer this question with complete accuracy. All other methods resemble fortune telling. The size of the baby’s bones and head, even on an ultrasound, can indicate weight only indirectly, because there are children with long legs (like mom), but thin or with a big head (like dad).

Doctors themselves claim that the accuracy of determining fetal weight can be affected by the quality of visualization during ultrasound. If a woman is overweight, has extra pounds, or fat deposits on her stomach, then the error will increase. If a woman's pregnancy occurs against the background of oligohydramnios, the likelihood of a more significant error than 14% of body weight also increases. It is more difficult to calculate the weight of babies during pregnancy with twins, especially over long periods, because the limbs of one baby on an ultrasound can easily be mistaken for the limbs of another, as a result of which a significant error can creep into the predictions of the babies’ body weight.

If a child has developmental pathologies (hydrocephalus, microcephaly, gastroschisis), it is difficult to determine his expected weight, because the dimensions important for drawing up mathematical equations will not reflect the child’s real weight.

Reading time: 5 minutes

Every expectant mother should know the height and weight of the fetus by week of pregnancy, and other sizes of the child in the womb. Doctors determine the standards, and the pregnant woman is informed about the actual parameters when undergoing screening. In general, generally accepted criteria are more conditional and depend on the individual physical characteristics of biological parents. Information about what the baby's weight may be by week of pregnancy is very important, so it is necessary to measure the abdominal circumference in a timely manner. However, not all women in an “interesting position” can calculate such parameters.

What determines the weight of the fetus during pregnancy?

When a woman does not control the weight gain of her unborn baby, it is possible that oxygen starvation of the fetus may occur, which is fraught with dangerous consequences for health. If the weight of the fetus by week of pregnancy does not correspond to the norms, in case of too much, doctors do not rule out the occurrence of diabetes mellitus, while a shortage is observed when pregnancy fading, reduced immunity.

If we talk about physiology, large parents develop a large fetus and vice versa. However, women who are overweight and have an unhealthy diet should be especially careful, since excess fat disrupts the normal size of the embryo. In the latter case, we are talking about intrauterine diseases that need to be diagnosed in a timely manner using an unscheduled ultrasound. Everything about the embryo depends on other factors, such as:

• lifestyle and nutrition of the expectant mother;
• number of fetuses in the womb;
• maternal illness;
• genetic features;
• presence of bad habits.

How to calculate a child's weight

To correctly calculate weight by week of pregnancy, it is important to know the length of the child’s hip, head circumference, chest diameter, and biparental head size. Using these parameters, doctors can implement a special Hadlock method, appropriate in the 1st and 2nd trimester of pregnancy. At a later stage, the obstetrician determines the weight gain of the fetus by week, having only 2 indicators available - abdominal circumference and height to the fundus of the uterus. The expectant mother can track the dynamics of growth at home, using a special calculation form.

Formula for calculating fetal weight

With each obstetric week, the fetus gains grams, and the main task of the expectant mother is to find out the approximate value and respond in a timely manner if pathologies are suspected or present. In the latter case, it is necessary to operate using the ultrasound method, as it is the most informative. The weight of an unborn child is determined using the following formula: (A+B+C)/3. However, such a publicly available calculation does not work with a large baby and in the later stages of pregnancy and is inaccurate. The explanation of the formula is presented below:

• A is a product in which the first and second factors are the height of the uterine fundus and the abdominal circumference;
• B – the sum of the height of the uterine fundus and abdominal circumference, divided by 4, and then multiplied by another 100;
• C – subtract 11 (if the woman has thin bones) or 12 (if the bones are large) from the height of the uterine fundus, multiply the result by 155.

Baby's weight according to ultrasound

A woman will gain kilograms every month, and the weight of the fetus will also increase over the weeks of pregnancy. The exact weight and size of the uterus can be determined during an ultrasound and monitored at the next screening. The monitor screen clearly shows the parameters of fetal length, approximate weight (calculated in grams), the presence of multiple pregnancies and potential pathologies of intrauterine development. Women with normal weight gain may panic, but if they are underweight or overweight, the patient comes under strict medical control, and hospitalization cannot be ruled out.

Baby's weight by week of pregnancy

After successful conception, a woman should register her pregnancy as soon as possible. Determining the length of the embryo in the early stages is very problematic, and the approximate weight is no more than a couple of grams. If the pregnancy proceeds without pathologies, the baby’s parameters reach average values, a table of fetal weight by week is available. Here is how the size of the fetus increases by month of pregnancy (with errors) without taking into account the placenta and amniotic fluid:

Serious deviations

Routine ultrasound examinations are carried out to determine the weight of the fetus by week of pregnancy. If the expectant mother does everything correctly, the babies are born strong and healthy. When the weight is insufficient, fetal movements slow down, and abnormal processes in the child’s body progress under the influence of pathogenic factors. Serious deviations are presented below and require timely correction in conditions of mandatory hospitalization:

1. Fetal swelling associated with increased bilirubin levels. The result is hemolytic disease of the newborn. In this case, the fetal parameter being studied reaches its maximum size.
2. Improper nutrition of the mother, as a result of which the fetus gains excessive weight, is at risk. The lack of nutrients and the presence of a voluminous fat layer creates favorable conditions for extensive congenital pathologies of the baby.
3. High rates of growth and weight gain of the embryo at different stages of pregnancy indicate internal diseases, alternatively it could be congenital diabetes mellitus, extensive pathologies of the liver and kidneys.
4. The womb influences the development of the embryo. A low-weight fetus may suffer from progressive hypoxia, which, after the baby is born, leads to increased intracranial pressure and other equally serious diseases.

How to gain weight for the fetus during pregnancy

If the norm of fetal weight by week does not correspond to generally accepted table values, and the characteristic deviation is repeated every month, do not panic unnecessarily. It is possible that the biological parents are large, and the child “has someone to be like.” However, it won’t hurt to be examined once again in a hospital setting; let the doctor calculate the indicated parameters using ultrasound, weight gain, and rule out the development of extensive pathologies. To ensure that the embryo gains extra pounds as expected, here are valuable recommendations from a specialist:

1. A pregnant woman should balance her daily diet, consume more vitamins and minerals, and get them from food.
2. The expectant mother needs to take multivitamin complexes that promote smooth intrauterine development without pathologies.
3. It is important to control the daily nutrition of a pregnant woman, excluding harmful cholesterol, preservatives, and questionable food products from the daily menu.

Video

The information presented in the article is for informational purposes only. The materials in the article do not encourage self-treatment. Only a qualified doctor can make a diagnosis and make recommendations for treatment based on the individual characteristics of a particular patient.

Pregnant women often wonder about the weight of the unborn child, since the method of delivery and whether the child is growing normally depends on this. Let's look at how the estimated fetal weight is determined from the table. It is worth noting that some women do not delve into what fetometry gives, but simply want to know the measurement indicators out of simple curiosity. It is precisely because of the increased interest in this issue that obstetricians propose to determine the weight of the fetus.

A variety of calculation methods are offered. These include simple arithmetic calculations and automatic calculation formulas. And in each case, a table is required. After 19-20 weeks, the expectant mother will be able to find out the sex of her unborn baby, but the weight has not yet been determined.

Basic methods

Determination of fetal weight is not carried out at all stages of pregnancy. And from about 19-20 weeks. Why? Yes, because until the 19th-20th week, babies have a small, approximately all the same weight. And fetal fetometry will give little information regarding this factor. But measurements of BPR and LZR are more important here.

Fetal weight is most often determined by indicators of the mother and child, which are determined during ultrasound measurements of the pregnant woman and fetus at 19-20 weeks. This data contains photometry determined by the ultrasound specialist and the corresponding table.

The main methods that allow you to more or less accurately determine the expected weight of the child at the end of the pregnancy period include the following formulas:

• Lankowitz;
• Bublichenko;
• Johnson
• Yakubova;
• Jordania;
• using ultrasound.

Determine the expected kilograms that the child will have at the time of birth using the following parameters:

• the weight of the expectant mother herself;
• growth of the expectant mother;
• the coverage of her abdomen at a given stage of pregnancy;
• the height of the uterus, or rather its bottom, of the expectant mother.

Sometimes when calculating the weight of a future baby, other parameters are required. But this is needed extremely rarely; all the necessary data is contained in the fetometry produced by the device. In addition, modern ultrasound equipment has software capabilities for automatic calculations. And these programs have everything that is necessary for this; fetal fetometry gives all the necessary dimensions, including LZR. It is most often included in the tables from 19-20 weeks of pregnancy.

Well, it’s clear how programs work in ultrasound machines. But how is the weight of the fetus determined by linear parameters measured by a gynecologist? Let's try to figure out how calculations are made using the proposed formulas:

• Lankowitz formula. The mass of the unborn baby is determined as follows. All the parameters of the expectant mother listed above are summed up, and then the result is multiplied by 10. The approximate mass is obtained. Moreover, this result gives a fairly accurate result.
• Bublichenko's formula. To calculate the mass of the future baby. Knowledge of the weight of the pregnant mother is required. This mass must be divided by 20. The result obtained will give the required mass of the future newborn.
• Johnson's formula. In this case, the weight of the fetus is determined by multiplying the difference between the height of the uterus and the number 11 by 155. Here 11 is a conditional indicator if the weight of the expectant mother does not reach 90 kg.
• Yakubova's formula. D To calculate the baby's weight at birth, the height of the mother's uterus is added to the circumference of her abdomen. The result is divided by 4 and multiplied by 100.
• Jordania formula. The mass is determined by multiplying the length of the abdominal circumference with the height of the uterus, or rather its bottom.

All. Of course, good, but how to find this very bottom height? Well, how to carry out all other measurements correctly?

Measurement rules

For measurements you need a measuring tape, which is used by cutters. Every housewife has one. Further:

• Abdominal circumference is measured at the navel line.
• The height of the fundus of the uterus is measured as follows: the end of the measuring tape should be placed on the upper extreme part of the pubic movable joint, and measure the distance to the fundus of the uterus. For minimal error, you need to draw the edge of your hand along the uterus to more accurately determine its fundus.

Only distortions in the measurement results are possible, and often these distortions do not depend on the error of the measurer. For example, if the expectant mother is expecting not one child, but twins or triplets. Errors are also possible in cases of polyhydramnios or when a woman is overweight.

Determination by ultrasound

The most accurate calculation of estimated birth weight, as already mentioned, is done by ultrasound. Ultrasound photometry is performed for many parameters from the very first weeks. But for these calculations, the dimensions contained in the fetometry done on an ultrasound scan at 19-20 weeks are important. The calculations carried out by the ultrasound machine help not only to predict the answer to this question with high accuracy, but also to compare the compliance of all received data with the deadline and standards. A table has been created with the specified standards for ultrasound. To obtain results, a protocol is required. Then you will need the following dimensions and data:

• gestational age in weeks;
• BPR heads;
• LZR or baby's head circumference;
• OB – baby’s abdominal circumference;
• thigh length;
• chest diameter.

Calculating the baby's weight based on ultrasound data does not depend on the weight of the water, the position of the fetus in or even the number of fetuses. Next, a program for calculating the baby’s mass runs, producing the result. The calculated fetal weight using ultrasound is closer to the actual weight the baby will be born with. How are the measurements obtained used for such calculations? It should only be borne in mind that photometry in the tables displays only average parameters, which often do not coincide with a particular child. Deviations can be for any of them. Using all the measurements that are made for each fetus at different stages of pregnancy, the calculation is carried out.

The baby's weight norm, which is given by the ultrasound table, is far from ideal, because it depends on a much larger number of parameters. And genes and the number of children play a significant role here. Each twin baby weighs significantly less. Here is one such standard listing, which is given in a table for different weeks of pregnancy.

Fetal photometry for some weeks (table)

Normal baby weight at birth

This figure varies greatly: from 2.5 to 4 kg.

If the baby's weight at birth is less than 2.5 kg, then a diagnosis is made: malnutrition. She was still in the womb and means that the placenta was not coping with its function. If a newborn weighs more than 4 kg, then it is a large baby. He belongs to the risk group and needs more careful monitoring in the future.

Why is mass determination necessary?

When the child is expected to be very large, with a large mass, then there is only one way out: a caesarean section. Although there have been cases of the birth of a child weighing more than 5 kg naturally.

And for a child with too little weight, it is necessary to prepare all measures so that after birth the baby receives everything that he lacked in his mother’s womb. Such babies are also often delivered by caesarean section. But a small baby’s weight is not always a sign of prematurity or pathologies. This parameter of the baby is also influenced by the hereditary factor.

So if the child’s fetometry has deviations of any size, this is not yet a reason to worry. The doctor will definitely tell you all possible diseases.

The size of the baby largely determines how the birth will proceed, so calculating the weight of the fetus for many expectant mothers becomes almost a priority task. Obstetricians and gynecologists use several formulas that allow them to calculate the expected. It is worth noting that the data from such calculations are relative, since they depend on many features, including the anatomical structure of the mother, the amount of amniotic fluid, the position of the fetus in the uterus, etc.

Formulas for determining weight:

1. Coolant x VDM

   In this formula, the main quantities are the abdominal circumference and the height of the uterine fundus. So, for example, if at 32 weeks the abdominal circumference is 84 cm, and the second indicator is 32 cm, then the approximate weight of the fetus is 2688 g. It is worth repeating once again that the results of such calculations are relative, and the error can be up to 200-300 g.

2. (coolant + VDM)/4 x 100

   This formula also allows you to calculate the weight of the fetus during pregnancy. To do this, two indicators (abdominal circumference and height of the uterine fundus) must be added, divided by four and multiplied by one hundred. So, with the given parameters, the weight of the fetus will be 2900 g.

3. (VDM – 12 or 11) x 155

   The third formula shows how to calculate the approximate weight of the fetus, taking into account the woman’s physique. According to Solovyov’s formula, a certain index is subtracted from the height of the uterine fundus (12 if the woman’s wrist circumference is more than 12 cm, 11 if less), and then the resulting number is multiplied by 155. As a result, for this example, the weight of the fetus will be 3100 or 3255 gram depending on the body structure of the expectant mother.

Determination of fetal weight by ultrasound

The most accurate data can be obtained by calculating the weight of the fetus using ultrasound. An ultrasound examination allows you to determine not only the weight of the baby, but the correspondence of its individual sizes to the gestational age. In order to calculate, there is a special calculator. If you enter all the ultrasound examination data, you can get a result that is closest to reality.

By making calculations using various formulas and taking into account the results of ultrasound, you can calculate the most accurate weight of the fetus at birth. It is worth remembering that each organism is individual, so if the results obtained are higher or lower than normal, it is too early to panic. As a rule, the norms can be strictly applied only to the first half of pregnancy, when the fetus is still very small, while in the third trimester the error can reach 500 g.

Fetal weight is an important indicator of its development. This criterion is included in the list of diagnostic parameters, on the basis of which the doctor makes a conclusion about the course of pregnancy, the presence or absence of abnormalities, and prescribes appropriate examinations. The baby's development occurs quite quickly. This is facilitated by the enlargement of the uterus, the size of which increases 500 times during the gestation period. The weight of this organ at the last stage of pregnancy reaches 1 kg 200 g, despite the fact that its initial weight is 50 g.

The baby's weight is monitored using ultrasound. This diagnosis is carried out from the middle of the first trimester. The size of the embryo, which is still too small to be seen even by an ultrasound machine, does not allow this procedure to be carried out at an earlier stage. At different stages of pregnancy, the fetus gains up to several hundred grams. Let's look at this process in more detail:

1. On the 14th day of the cycle, the mature egg moves from the ovary to the fallopian tube. Over the next 24 hours, she retains the ability to fertilize. If contact with a sperm occurs during this time period, the egg will be fertilized. Next, division will begin and on the fourth day it will move into the uterine cavity.
2. After 3 weeks, the egg is implanted, this moment is considered the onset of conception. The outer cells of the embryo have villi, which attach it to the woman's blood vessels. This is how the placenta is formed. The internal cells will subsequently form tissues and organs. The length of the embryo at this stage is 6 mm. It is located in a bladder that is filled with liquid.
3. From 5 to 6 weeks, the formation of the spine, nervous system and brain occurs. The development of the digestive system, mouth, and chest begins. By the end of the 6th week, the heart begins its work, in which 4 sections function. In the head area, 4 depressions are formed, which will later turn into ears and eyes. The formation of the circulatory system occurs. The embryo develops 4 formations from which limbs will form.
4. With the onset of the 7th week, the length of the unborn baby reaches 13 mm. His head has already been formed, but so far it has disproportionately large parameters in relation to the body. You can make out a face. Fingers begin to appear on the limbs. At this stage, cells are formed from which the skeleton will develop. The central nervous system is fully formed. There are internal organs, but their development is not yet complete.
5. With the arrival of the 8th week, the length of the fetus is 2.5 cm. The main organs have already completed their formation. The outlines of the mouth and nose are visible on the face, and a tongue is formed. Increased size of arms and legs. The toes are fairly well marked, but there are still membranes between them.
6. At week 12, the fetus increases to 65 mm, its weight is 18 g. You can see the ears on the head. The baby now has eyelids, allowing him to close his eyes. Marigolds are noticeable on the fingers. Muscle tissue develops, the child begins to move actively.
7. From the 14th week, the placenta begins to perform one of its tasks and provides the fetus with nutrition. The head size is still disproportionately large. The neck is different. The body is covered with lanugo fluff. The baby has eyebrows and eyelashes. His bones become harder, and the joints of his limbs are formed. The degree of development of the genital organs allows one to determine gender. The child acquires the skill of thumb sucking.
8. By week 16, the organs and systems of the fetus are formed. It reaches 16 cm in length and 135 g in weight.
9. At 20 weeks of pregnancy, the weight of the fetus is 340 g, length - 25 cm. The child develops hairs and the base of teeth. Organs that have already formed increase in size. Kidney activity begins. The limbs acquire dimensions proportional to the body. The child is quite active. At this stage, mom feels him well.
10. In the period from 21 to 24 weeks, the baby weighs 570 g, his length is 33 cm. He acquires new skills and can already squint, frown, hiccup, cough, push, roll over, clench his fists. Sweat glands appear in the skin. The fetus has sufficiently developed auditory receptors. He is able to distinguish sounds, among which his mother’s voice and heartbeat stand out. The child spends a certain part of his time in a state of sleep. His tongue is already able to distinguish tastes.
11. Until the 28th week, the baby gains 1 kg, his height reaches 37 cm. The formation of adipose tissue begins. The development of the cerebral cortex has completed. The lungs continue to form. The child is able to react to external stimuli and even cry.
12. When the 30th week of pregnancy arrives, the fetus weighs about 1.5 kg and is 40 cm tall. At this stage, it is preparing for birth and is in a suitable position.
13. By week 36, the baby gains 2.5 kg and grows to 46 cm. Thanks to adipose tissue, it acquires a rounded shape. The color of the skin becomes pink. The baby has acquired a grasping reflex and can lift his head and turn. Lung formation is complete. The child has a reaction to light.
14. By the 40th week, the baby’s weight is 3.4-3.5 kg, height – 50-51 cm. Vernix lubrication spreads throughout the body. The head descends into the pelvic area. It should be noted that these parameters are relative. Each pregnancy must be considered individually.

What determines the weight and height of the fetus by week of pregnancy?

Several factors influence fetal weight. One of them is the mother’s health status and her diet. Full growth of the baby is possible only with optimal insulin concentration. This substance promotes the formation of the fat layer, as well as all cells and tissues. If there is an excessive content of this element in the mother’s body, the child is born with a large weight. This mainly applies to women suffering from diabetes.

Anemia during pregnancy causes placental insufficiency. This can lead to developmental delays and the birth of an underweight baby. At 34 weeks of pregnancy, the normal weight of the fetus should reach 2150 g. If the baby weighs less, the doctor may suspect developmental abnormalities. But to confirm or refute this, it is necessary to conduct a certain examination.

The size of the fetus also depends on the condition of the placenta. Its growth is influenced by uteroplacental blood flow. If the function of this organ is impaired, the fetus is not provided with sufficient quantities of nutrients and oxygen. As a result, the process of weight gain and growth slows down.
Disturbances in the condition of the placenta or in the health of the expectant mother do not always negatively affect the child’s body weight. With adequate therapy, the fetus develops according to established standards. If the baby’s weight is less than the required value, but no abnormalities are observed, treatment is not prescribed.

One of the factors influencing growth is heredity. The term “constitutionally low birth weight fetus” is applied to such children. If the parents have a thin build and short stature (up to 160 cm), the baby’s low weight is physiological in nature. Such a child has no pathologies.
But if underweight is due to any disorder, the woman should be under the careful supervision of specialists. With placental insufficiency, developmental delay (hypotrophy) is observed. There are two types of this condition:

• symmetrical;
• asymmetrical hypotrophy.

In the first case, all organs lag behind in development, in the second, certain organs correspond to the deadline, while others lag behind in development.

The weight of the child is also influenced by such factors as: heredity, the woman’s lifestyle, the number of fetuses, various features of pregnancy and the age of the mother. Women under 18 and over 35 years old require special monitoring. They are most often diagnosed with child malnutrition. When 36 weeks of pregnancy approaches, the weight of the fetus is 2.5 kg, height 45-46 cm. If the baby appears with these parameters before a certain period, he is considered full-term and fully ready for life outside the mother’s womb.
If the placenta does not fulfill its function, the expectant mother is prescribed vasodilating medications, the action of which is aimed at normalizing the blood supply to the blood vessels of the fetus and uterus. Medicines are also used that increase the child’s resistance to oxygen deficiency.

Exceeding the weight limit

Exceeding the norm also does not always indicate the presence of anomalies. Excessive baby weight, which is 4 kg or more, can be explained by the large physique of the parents or the mother’s excess nutrition. If a woman is diagnosed with diabetes mellitus or other endocrine system abnormalities, a large weight of the child should be considered as a complication. This situation can also arise as a result of postmaturity. If at 35 weeks of pregnancy the weight of the fetus exceeds 2390 g, it can be said that the baby will appear large.
The baby's heavy weight complicates the delivery process. If his head exceeds the size of the woman's pelvis, the doctor may decide to perform a caesarean section. Too large sizes cause premature release of amniotic fluid and weak labor.

Home methods for calculating weight

You can determine the baby’s weight yourself at home. There are several options for this:

1. One of them involves multiplying the abdominal circumference by the height of the uterine fundus. It must be taken into account that the result may be affected by the amount of amniotic fluid, the position of the fetus in the uterine cavity, and its physique. But despite this, this method is considered to be the most reliable.
2. According to the following method, you need to divide the abdominal circumference by the height of the uterine fundus. The result obtained should be divided by another 4 and multiplied by 100. This option is primarily not used as an independent calculation method, but is used to confirm existing indicators.
3. You can also determine the weight of the fetus using the Solovyov method. Its peculiarity is that the size of the mother’s wrist and her physique are taken into account. This method may seem unreliable; some women have doubts about the ability to calculate a child’s weight using the wrist. But at the same time it gives true results.

First of all, you need to determine the index. If the wrist of the expectant mother has a circumference greater than 16 cm, the index value will be 12. If the circumference is less than 16 cm, this indicator will be 11. Next, the index is subtracted from the height of the uterine fundus, the resulting number is multiplied by 155. At 31 weeks of pregnancy, the weight of the fetus should reach 1.5 kg. The Solovyov measurement method will help you check how much the baby’s mass corresponds to this parameter. To obtain the most reliable results, it is recommended to determine weight using all three methods.

Weight determination by ultrasound

In a medical institution, fetal weight is determined by ultrasound diagnostics. The doctor focuses on the following indicators:

• gestational age;
• biparietal parameters of the head (the space between the two widest areas);
• length of arms and legs;
• fronto-occipital parameters;
• abdominal and head circumference.

If abnormalities are detected, to clarify the diagnosis, a Doppler study of the baby’s blood vessels, placenta and umbilical cord is prescribed, which allows one to get an idea of ​​the speed of blood flow. Cardiotocography is also necessary.

Based on the results of this study, the doctor monitors the fetal heartbeat as a response to uterine contractions. For example, the weight of the fetus at the 33rd week of pregnancy should reach 1900. If there is a lag from this norm, this is an indication for additional research.

Fetal weight by week of pregnancy: table

Conclusion

Tracking fetal weight is one of the main procedures during pregnancy. Based on the baby’s parameters, one can judge his development. And also promptly detect deviations if they occur. But you should not immediately worry if the doctor says that the child is underweight or, on the contrary, exceeds the norm. Such phenomena may arise as a result of heredity or the characteristics of pregnancy. Each case should be considered individually. And if disturbances in the child’s development are detected, the use of medications will help normalize the condition and a healthy baby will appear at the appointed time.
Video: fetal development by week