Fetal weight by week of pregnancy

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

Many mothers-to-be are very curious about how their baby develops. After all, its growth and changes are a kind of mystery. The fetus is hidden inside the mother's body, and she will be able to see it only after childbirth. But far from idle curiosity pushes women to find out what is the height and weight of their offspring. The size of the fetus can tell a lot about its he alth and development, and also allow you to more accurately determine the gestational age.

How to find out the size of the fetus

The most common method that allows you to evaluate several measurements of the baby's body and its weight is ultrasound. The fetus is measured by many parameters. For example, BDP, that is, the biparietal size of the head, is the distance from one parietal bone to another. In fact, this is the width of the head. This is just one of the parameters that allows you to estimate the approximate body weight. In addition to it, the circumference of the abdomen and the length of the femur are taken into account. Up to 28 weeks, BDP allows you to determine the gestational age with an accuracy of up to a week. Later headthe child grows at an individual pace, so the accuracy of the calculation for this parameter is reduced.

Embryo growth is measured excluding legs. This is KTR - coccygeal-parietal size. The legs are bent, so the most reliable result is obtained when measuring the head and torso. When measuring the fetus, doctors take into account the proportionality of all sizes. If not a single dimension is strongly out of proportion, the baby develops correctly.

In the later stages, the circumference of the abdomen and the height of the fundus of the uterus carry important information about the size of the fetus. This also allows you to roughly estimate the weight of the baby. There are special mathematical formulas for this since the middle of the last century.

Jordania Formula

In order to use this formula, you need to know the circumference of the pregnant woman's abdomen and the height of the fundus of the uterus. Usually all this information is in the medical record. The belly is easy to measure with a tape measure. But the height of the bottom of the uterus for calculations, you can take the average for weeks. The weight of the fetus can be obtained by dividing the girth of the abdomen by the height of the uterine fundus.

True, sometimes to refine these calculations, coefficients are introduced that include the weight of the mother, the girth of her wrist. This is due to the fact that the size of the abdomen can depend not only on the build of the baby, but also on the physique of the woman and her fat layer. The thickness of the wrist, on the other hand, speaks about the structure of the bones of a woman and allows you to evaluate her physique.

Lankowitz formula

This is a more accurate formula that takes into account many more indicators. To get the result, it is necessary to add the height of the pregnant woman in centimeters and her weight to the girth of the abdomen and the height of the uterine fundus. The resulting amount is multiplied by 10. True, this method of calculation also has errors. In 25% of cases, he is wrong by 200 or even 500 g.

Terms and errors

In the early stages, for example, in the first trimester of pregnancy, noticeable deviations in the weight of the fetus by weeks, with the correct structure of his body, may indicate that the term is determined incorrectly. Based on this, ideas about the duration of pregnancy are usually clarified. After all, initially it is calculated in two ways.

The true gestational age is determined from conception. But not all women know the date of ovulation. But almost everyone perfectly remembers the date of the beginning of the last menstruation. It is from her that the obstetric period is considered. This is the gestational age, which exceeds the actual gestation time by 2-3 weeks. Most often, ovulation occurs exactly 2 weeks after the start of the cycle. True, both the duration of the cycle in women, and its other individual characteristics affect when conception actually occurs.

What determines the weight of the fetus

The weight of the fetus by week of pregnancy at the very beginning is usually the same for everyone. The more developed the fetus becomes, the more individual differences appear in it. He althy full-term babies are born very different, sometimes their weight can vary by one and a half to two kg. Anyway, children weighing 3 kg and 4.5 are both normal.

Baby's weight may depend on body sizeparents. Genetics predetermine the physique of the child, and large parents can have a large baby. Moreover, with a high probability, the weight of the baby will be close to the weight of the father and mother at birth. So there are norms for fetal weight by week of pregnancy, but they should not be strict and always have some variation.

Low weight

But many other factors also play a role. Strong deviations from the norm of weight in the fetus by weeks can indicate pathologies. Mom's illnesses and bad habits affect the baby's body weight. Losing weight can be a dangerous sign of a missed pregnancy or be observed with a decrease in immunity.

In addition, this can be observed during hypoxia. The lack of oxygen is dangerous for the fetus, it can subsequently lead to pathologies in the brain, increased intracranial pressure.

Big weight

Excessive weight is not always a reason for joy that a hero will be born soon. Sometimes this can be observed with diabetes in the mother. Other causes of fetal overweight are swelling with elevated bilirubin levels. This is associated with a dangerous disease - hemolytic disease of the newborn. Most often, this disease is observed with Rhesus conflict. It can lead to many pathologies in the baby's body, such as brain damage, which can even lead to mental retardation.

Improper nutrition of the mother leads to the fact that the baby has a large fat layer, but at the same time receives less nutrients. This, too, will not have the best effect on his body.

The reason for the birth of a large baby can be the individual characteristics of the mother's body and the course of her pregnancy. For example, a large, well-developed placenta provides the baby with more nutrients and faster growth.

Having a baby that is too large can be dangerous, because it is more difficult for him to pass through the narrow birth canal, therefore, the likelihood of injury to the child increases. For the mother, this can also threaten a caesarean section or an episiotomy.

Multiple pregnancy

Not only diseases and pathologies affect the change in the weight of the fetus by weeks. An important factor is the number of fetuses in the womb. Usually, the more of them, the less the weight of each of them. After all, carrying several large babies would be an impossible task for the mother’s body! It is necessary to provide food for everyone at once, and the place in the uterus is limited.

Therefore, with multiple pregnancies, babies are often born prematurely. If twins still have a chance to be born later than 37 weeks, then with more babies they are born even earlier. True, these children, with small stature and weight, can be full-term and have fully formed signs characteristic of a he althy baby. For example, they do not have structural features of the ears, genitals, the navel is in the middle of the abdomen, and not below. In special cases, for example, when there are as many as five fetuses, they can be born prematurely, for example, at 26 weeks with a weight of 1 kg.

First trimester

The weight of the fetus by weeks begins to be calculated only from the middlefirst trimester. The fact is that the embryo is too tiny to be able to estimate this parameter with sufficient accuracy. For example, at week 8, the embryo weighs 1.5 g. To make it easier for the mother to imagine what size and shape the body of her unborn child has, sometimes visual comparisons are made with berries, nuts, and vegetables. For example, at week 8, the embryo resembles a cashew nut in weight and body curve. At the 11th week, his weight reaches 10-15 grams. Depending on the term, the baby will add several tens, and then hundreds of grams per week.

Second trimester

This is the period from 13-14 to 26 weeks. The norms of the weight of the fetus by weeks in the second trimester indicate that it is during this period that it turns from a tiny creature into a man, whose weight can reach 850-1000 g and which has pronounced individual facial features. The mother's belly during this period increases and becomes noticeable. Weight gain in a pregnant woman is much higher than the weight of the fetus, for example, it can be 6-7 kg. This shouldn't be embarrassing. The uterus grows together with the child, it is filled with amniotic fluid, in which the baby still moves quite freely. The mother's blood volume also increases. In addition, the fat layer is also growing, which protects the stomach from injury and cold, and is also a reserve for the upcoming breastfeeding.

At 24 weeks, the weight of the fetus is from 550 to 750 g. Is it a lot or a little? If we compare this mass with the body weight of a newborn baby, then not so much. But if we remember thatonce the baby was a fertilized cell … Almost half of the pregnancy remains until the birth, but if the baby is born at that time, it will be considered a premature birth, not a miscarriage. Thanks to modern medicine, these babies have a chance of survival. True, they are small.

Third trimester

This is the time from 27 weeks to delivery, which usually occurs at 40 weeks. The weight of the baby increases the fastest, by hundreds of grams per week. On the other hand, the fastest growth relative to the former occurred in the first trimester. The weight of the embryo during this time has increased hundreds of times compared to the weight of a tiny embryo. Now it increases only 3-5 times.

This is not only due to the active growth of the child's body, but also due to a significant increase in body fat. You may notice that premature babies look thin and have red wrinkled skin. A term baby is much plumper and has smoother skin. Fat not only contains a store of energy, but also serves the purpose of thermoregulation. First of all, it keeps the child from hypothermia. Of course, if we are talking about the fat layer within the normal range. Overweight babies can have he alth problems. The weight of the fetus at 29 weeks is from 1300 to 1500 g. And this is already a lot.

Fetal weight at 30 weeks is 1600-1650 grams. His height will already be 40-41 cm - only a fifth less than at birth. This means that the baby is stilllooks skinny.

Ultrasound is usually prescribed at 32-34 weeks. Fetal weight at 32 weeks usually reaches 1800-1850

Research at this time is due to the fact that the baby usually already takes the right position before birth - the vast majority is in cephalic presentation, when the head is directed down towards the exit from the uterus. Determination of the state of the placenta, the height and weight of the fetus, the location of the pelvic bones make it possible to plan childbirth.

Fetal weight at 37 weeks can range from 2500 to 2800g. Babies born before 37 weeks are considered premature if they weigh less than 2500g and are less than 46cm tall.

Birth weight

And finally, children born at term, that is, around 40 weeks, or rather, from 38 to 42 weeks, on average, have a weight of 3100-3400 for girls and 3400-3600 for boys. Babies whose weight reaches 4 to 5 kg are considered large, and those that weigh more than 5 are considered giants. Usually these children are also large, for example 56 cm.

The most important thing is that the child becomes loved and desired, then it will be possible to overcome any hardships associated with his small or too large weight. And during pregnancy, it is best for mothers to eat he althy food, but not to diet, so that the child receives all the substances necessary for the development of the body.