Fetal head circumference by week: table

For all women, pregnancy is a special life stage. At this time, the expectant mother experiences new sensations and, on the other hand, learns her essence. Along with positive emotions and fantasies about the future baby, a young mother has to undergo many consultations and take a lot of tests. Such visits to the clinic sometimes make you nervous. But tests are necessary to monitor the normal growth and development of the baby in the woman’s tummy.

When ultrasound is needed

When the expectant mother comes to see her doctor, they explain to her the need and timing of the observations under ultrasound. Two types of ultrasound are distinguished : screenings and selective examinations. Screening is called a mandatory examination of all pregnant women using ultrasound at certain times. Usually, a planned ultrasound examination of the expectant mother takes place from 10 to 12 weeks, from 22 to 24 weeks, at 32 and 37-38 obstetric weeks of pregnancy. When conducting this type of examination, fetal size and their compliance with the norms, gestational age, uterus and placenta are measured. Selective studies are prescribed by your doctor if you suspect a pregnancy complication. In the case of determining the pathology of pregnancy, such examinations can be carried out an unlimited number of times.

Fetometry - what is it and why

One of the important procedures is fetometry. When conducting a doctor analyzes the size of the fetus and their compliance with the norm. The procedure is an ultrasound examination, the data of which the specialist checks with the tables of norms. Checking helps in time to detect defects and abnormalities in the development of the baby. When performing fetometry, the circumference of the fetal head is determined by weeks - the norm is an important indicator. By weeks, the doctor fixes the values ​​of ultrasound and draws conclusions about the health of the baby. When a doctor ascertains a smaller fetus than established for a given period, then they speak of a slowdown in fetal growth. If a lag of a couple of weeks is manifested over the course of pregnancy, then doctors are talking about intrauterine growth retardation. Such a delay can be caused by bad habits of the mother, internal infections, chromosomal abnormalities or placental insufficiency.

How does the circumference of the growing head of a normally developing fetus

The circumference of the fetal head by week is an important indicator of the development of the fetus in the womb of the mother. As you know, the head of a child in her mother’s stomach grows unevenly. At the beginning of development, its size significantly exceeds the size of the body. And by the end of pregnancy, the size of the fetus becomes uniform and proportional. If you trace how the circumference of the fetal head changes by week, you will notice that the largest increase occurs in the second trimester. It is from the 15th to the 26th week of pregnancy that the head circumference of the baby increases by an average of 12-13 mm. This increase occurs every week. With a further increase in gestational age, the growth of head circumference slows down. By the end of the third trimester - about a month before the birth of the baby - this figure becomes the most by 12-15 mm.

How to measure crumb head circumference

In order to measure the circumference of the fetal head by weeks, regular diagnostics are used using an ultrasound machine. The study is carried out by a specialist in several projections to obtain the most correct and accurate result. In addition to diagnosing the head circumference, the doctor diagnoses such fetometric indicators as biparietal (BDP) and sagittal size, hip bone length, abdominal circumference, fronto-occipital (LZR) size and others.

The table of norms used for diagnosis helps a specialist determine fetal development and potential abnormalities. If the doctor finds significant deviations from the norm, then the woman is offered to have an abortion.

Formula for calculating

The circumference of the fetal head by weeks is determined by the same principle as the biparietal size: it is measured by a method such as computer planimetry, or by the formula. Pre-determined biparietal and LZR head size. The formula has the following form: OG = 1/2 * (LZR + BPR) * 3.1416. This indicator is rarely used to calculate the weight of the fetus and does not depend on the shape of its head.

The value of the head circumference indicator of the child

What can an indicator like a fetal head circumference by weeks tell a doctor? The table of norms for this indicator has boundaries. If they are exceeded, this indicates the presence of developmental disorders. In this case, the main task of the doctor becomes the earlier identification of deviations and their correction. For example, an increase in head circumference may indicate a disease such as hydrocephalus. The disease manifests itself in the accumulation of fluid in the cavities of the ventricles of the brain. Such a process leads to an increase in pressure inside the skull and, as a result, to a decrease in the volume of the brain. Immediately after birth, the baby is punctured. Using the procedure, the accumulated liquid is removed and the condition of the child is facilitated.

The value of indicators for childbirth

In most cases, the excess of parameters is attributed to the individual characteristics of the crumbs. For example, if the parents are large, it is assumed that the child will also be large. As already mentioned, the table shows the circumference of the fetal head by weeks of pregnancy. An increase in the rate at the end of pregnancy can lead to problems in the birth process. For example, to rupture of the perineum. An episiotomy is made, that is, a small incision to facilitate labor.

The importance of the indicator

So, determining head circumference indicators at different stages of pregnancy and comparing other indicators helps the doctor to identify pathologies in the development of the fetus, growth and development rates , as well as possible difficulties. A woman should not independently interpret or try to decipher the results of ultrasound diagnostics and draw conclusions about the baby’s health. The doctor takes into account multiple factors and observations, and only then makes an objective conclusion. It is important to remember that the development of each baby is individual and may not occur according to table values.

32 weeks - why it matters

An important stage in ultrasound diagnostics is the term in the 32nd week of pregnancy. Around this period, the fetus takes the correct position for the birth process - head down. The circumference of the fetal head (32 weeks of gestation) is approximately 283-325 mm. This period of pregnancy is quite significant. The little baby in the mother’s tummy is almost formed and even has eyelashes and eyebrows.

Fetal head circumference: table

As already mentioned, the expectant mother carries out the first important ultrasound diagnostics at 10-12 weeks of an interesting position. The table shows data starting from the 11th week of pregnancy. Calculation occurs from the day of the last menstruation. Tabular data for the 10th, 50th and 95th percentiles are presented. Most often, doctors focus on the 50th percentile, but fluctuations from 10 to 95 are considered the norm. Percentile is a percentage that is below a certain percentage in the sample. That is, the 50th percentile indicates that 50% of these values ​​are below this level.

Of course, for every woman, the state of a small miracle is more important than anything else. While the baby is still in the tummy, the only way to see it is ultrasound. The importance of the study of indicators of head circumference, height, weight and others is due to the need for continuous monitoring of fetal development. Such monitoring not only helps an experienced specialist to conduct pregnancy correctly, but also calms the expectant mother, who wants to quickly hold her baby in her arms.