Expectant mothers are always very interested in what weight their baby will be born with. Therefore, they are keenly interested in how much the crumb weighs while still in the womb. This question is also important for doctors. Although the weight of the fetus is called estimated, but even it allows you to learn a lot about the development of the baby. What is usually the weight of the baby in the mother's womb at different periods of pregnancy and what it depends on, we will tell in this material.
How does the baby grow?
At the very beginning of pregnancy, all crumbs, regardless of gender, race, heredity, grow in exactly the same way, adding millimeters and grams to their tiny weight every week. All embryos grow at approximately the same rate, and only then, when the individual characteristics of the little man begin to appear, differences begin to appear.
It is possible to measure the growth of the fetus even with the most modern ultrasound machine only in the second half of the first trimester. Until 8 weeks, only the diameter of the ovum is measured, and this criterion is considered the main one, indicating the growth of the embryo.
The size of the crumbs itself is not yet available for measurements, the only exception is the coccygeal-parietal size, but it does not provide a basis for calculating the weight of the embryo.
For the first time, it is possible to talk about the weight of the fetus when undergoing an ultrasound examination, starting at 11 weeks. 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 it 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, a period of their intensive growth and improvement begins. Gradually, the baby begins to stock up on subcutaneous fat, hence the rapid weight gain. The biggest increase awaits the baby in the third trimester.
In recent months, the child is already physiologically ready for birth, it remains only a little "to recover", all organs and systems are working. Since a fairly grown baby can no longer actively move in the uterine cavity, sleep and occasional unsharp movements in the cramped uterus become his main occupation. Over the past two months, the baby has been gaining the weight that he will have at birth, and only in the last days before childbirth, the weight gain almost stops.
From the end of the second trimester, female fetuses are gaining slightly less than baby boys. Therefore, in the third trimester, they almost always differ in more miniature forms, although this is not an absolute rule - there are girls who, by weight, can leave any little boy behind.
What affects mass?
The weight of the fetus is primarily affected by heredity. If mom and dad are big and big, then the probability that they will have the same "hero" is more than 90%. Miniature, short, skinny mom and dad usually give birth to a baby with low weight. It is rather difficult for any outside 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, this is food. If a mother eats well, in a balanced way, 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 fond of carbohydrates, cakes, baked goods, abuses vitamin complexes, even if she does not have a vitamin deficiency, then the child receives all this through the uteroplacental blood flow. The mother's weight is growing, 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, lacks 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 fetal weight. 70% of pregnant women who smoke give birth to children with underweight. In the same way, the fetus is affected by alcohol, drugs, and even the usual medications that the mother took during pregnancy. Mom's nervous stresses and worries, hard physical work, working conditions in hazardous industries adversely affect the baby's body weight.
Some chronic diseases that the expectant mother has also affect the weight of the baby. For example, with diabetes mellitus or gestational diabetes, which first manifested itself already during the period of gestation, there is a possibility of giving birth to a large or even giant baby, whose weight will exceed 5 kilograms. And the lack of fetal weight can manifest itself in chronic diseases of the kidneys, liver and heart in a woman.
The peculiarities of the course of pregnancy cannot but affect the weight of the child. If everything goes smoothly, then there is nothing to worry about. But a baby that develops in conditions close to extreme, against the background of a threat of miscarriage, with other complications of gestation, is unlikely to be a hero.
If the pregnancy is multiple, the 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 on her own.
Lankowitz formula
Experts consider this method of calculation to be the most accurate, although, unfortunately, it cannot do without errors. For calculations, a woman will need to look at her exchange card on the page of the last visit to the doctor. There she will find two important parameters for the calculation - her abdominal circumference (OJ) and the height of the fundus of the uterus (VVDM or VDM).
Both of these values are added, after which, in the resulting amount, the mother's weight in kilograms and her height in centimeters are added. The resulting number is multiplied by 10. For example: gestational age 30 weeks, abdominal circumference 110, fundus height - 30. Pregnant woman's height - 170 cm, weight - 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 - his real weight at this time already exceeds 3 kilograms.
Bublchenko's 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 with this method is large, it fluctuates within the kilogram, which is why obstetricians have recently tried not to use such a formula
Yakubova's formula
For these calculations, a woman who 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. WDM is added to the abdominal circumference, and the resulting sum is divided by 4 and multiplied by 100. For example, WDM - 30, abdominal circumference 100. (30 + 100) / 4 = 32.5. When multiplied by 100, you get 3250 gr.
Formula Jordania
To calculate again, you will 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, WDM -30, circumference - 100, it turns out that the estimated weight of the child is 3 kilograms.
Ultrasound
The most accurate calculations are those that are made by the sonographic method, that is, by ultrasound. To derive the estimated body weight of a child, special equations are used, which are compiled by the software of the scanning device, the most often used is the Headlock method.
As the necessary mathematical values for the equations, the sizes that the doctor-somnologist determines on the ultrasound are used. it biparietal 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 Headlock and Shepard):
- Shepard - Log10 BW = -1.7492 + 0.166 (biparietal size) + 0.046 (fetal tummy circumference) - (2.646 [(tummy circumference) X (biparietal size)] / 100).
- According to Headlock - 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 (biparietal size head) 2 + 0.0458 (abdominal circumference) + 0.158 (femur length) - 0.003343 (abdominal circumference multiplied by 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 "Estimated fetal weight" section. The margin of error for singleton pregnancy is 8 to 10%, when carrying twins, the error increases to 15%.
This method cannot be called accurate, as in a pharmacy, but medicine has not yet invented anything more precise.
It is on the basis of ultrasound data that all the currently existing norms of fetal weight by weeks and months of pregnancy have been created.
Rates at different times
What should be the body weight of a child who has not yet been born, it is difficult to say unequivocally, because we are all different - tall, short, thin and full. Babies in the womb also have personality traits. Therefore, there may be a scatter, 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 regard to 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 estimated weight, use tables developed by doctors from Germany to measure the weight of European-looking children in the early 90s of the last century. It is compiled taking into account the sex of the fetus.
Table of normal values for the estimated weight of babies of different sexes:
German tables, which are used all over the world, do not start at 23 weeks of pregnancy by accident. It is at this time that the formation of the body according to gender begins in children of different sex, which is why the weight gain in boys and girls begins to differ from each other. At an earlier date, this difference between different-sex babies 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 a period of 39-40 weeks with a weight from 3000 to 3800 g. However, those babies who are born with a weight of up to 3 kilograms, and those who at birth have more than 4.5 kg of weight, have neonatologists are not alarmed.
Midwives 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 the error (plus or minus 500 g at least), and secondly, babies grow "jumps", so at 34 weeks the crumb can upset the mother with a lag from the average statistical norms, and by 36 weeks to reach normal average or even close to the upper limit of the norm.
If the baby throughout all ultrasound examinations during pregnancy demonstrates a persistent excess of norms, they speak of a large fetus. The trend towards a large baby can be seen already in the second trimester. On the basis of one ultrasound, such a conclusion cannot be drawn, several studies are required over several weeks.
At the same time, attention is also paid to instrumental measurements - the circumference of the abdomen of the expectant mother and the height of the uterus. With a large fetus, WDM usually exceeds the norm (at 32 weeks with a norm of 32 cm, for example, this parameter is increased to 34 cm, and at 36 weeks instead of the prescribed 36 cm it is about 39 centimeters).
If the baby in the mother's womb lags noticeably behind the average values and for several diagnostic measurements "passes" only along the lowest border 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 fetal pathologies, including hereditary and chromosomal, intrauterine growth retardation, the presence or absence of intrauterine infections, Rh-conflict.
To do this, an ultrasound of an expert class is performed, an ultrasound scan, tests for infections, clinical blood and urine tests are performed. If necessary, the woman is sent for consultation with genetics and undergoing invasive diagnostics for the detection of chromosomal abnormalities.
Whether to agree to such measures is up to the expectant mother herself, especially since modern medicine is ready to provide a harmless but expensive alternative to invasive diagnostic methods - a prenatal DNA test by analyzing blood from the mother's vein.
A woman with a suspicion of fetal malnutrition is assigned regular monitoring of the baby's condition using cardiography (CTG), and additional treatment (sometimes in a hospital) is prescribed, which includes taking vitamins and drugs to improve uteroplacental blood flow. The estimated weight of the crumbs is monitored using intermediate ultrasound examinations.
Lagging behind the norms is not considered particularly dangerous if all the parameters of the baby are reduced symmetrically... Then it 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 on pregnancy and the approximate weight of the crumbs, they draw conclusions about the best way to give birth to a child.
With a large fetus, a cesarean section is often recommended, if the size of the fetus does not match the size of the pelvis, even if the baby's weight itself is normal, it is also recommended to perform a cesarean section.
Determination reliability and errors
As mentioned above, the most accurate is the method for determining the estimated weight of the baby in the mother's womb by ultrasound. According to the data received by American doctors from Florida, the error in the calculation according to Headlock was approximately 14% of the baby's body weight. In other words, the real mass differed from the predicted by the apparatus by 14% in one direction or another. This is the highest result to date.
The methods used by obstetricians 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 crumbs, you do not need to count anything. A computer program will help to calculate everything. The accuracy of the formulas (presented above and some others) is estimated at about 40-55%. Whereas on ultrasound, the accuracy of assessing the child's body weight is gaining almost 82%.
The most accurate method, as gynecologists like to say, is weighing. Therefore, those who want to find out how much a child weighs in grams, you just need to be patient and wait for the birth. They will answer this question with complete precision. All other methods resemble fortune telling. The size of the bones and the head of the baby, even on an ultrasound scan, can speak of weight only indirectly, because there are children with long legs (to the mother), but thin or large heads (to the father).
Doctors themselves claim that the quality of imaging during an ultrasound scan can affect the accuracy of determining the weight of the fetus.If a woman is plump, has extra pounds, fat deposits on the stomach, then the error will increase. If a woman's pregnancy proceeds against the background of low water, 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 for long periods of time, because the limbs of one baby on an ultrasound scan are easy to take on the limbs of another, as a result of which a significant error can creep into the forecasts of the body weight of babies.
If the child has developmental pathologies (hydrocephalus, microcephalus, gastroschisis), it is difficult to determine its estimated weight, because the dimensions that are important for compiling mathematical equations will not reflect the child's real weight.
Reviews
According to women's reviews on the forums devoted to pregnancy and motherhood, there are prevailing reviews about the erroneous determination of the child's weight before childbirth. Most young mothers emphasize that the weight was predicted to be less than it actually was, with the difference ranging from 100 grams to a kilogram.
Women who, by coincidence, did two ultrasounds on the same day in two different places on two different machines, claim that the calculations of the estimated body weight of the baby were noticeably different from each other. The closest "hit" to the truth was when a three-dimensional ultrasound was done.
All about the weight of the fetus by week, see the next video.
