Nasal bone norm at 12 weeks: indicators. Rates of first pregnancy screening: length of nasal bone

Modern medicine has made tremendous progress in examining pregnant women, and if previously it was considered quite sufficient to undergo ultrasound examination of the fetus and to pass some tests, these days this category of patients is under the watchful eye of specialists and subjected to periodic procedures and examinations. Basically, they are aimed at determining the state of the developing in the womb of the baby's mother and timely diagnosis of various anomalies. Including - ultrasound detection of such characteristics as the norm of the nasal bone, conducted after ten weeks of pregnancy.

The need to measure the nasal bones of the fetus

The pair, quadrangular form of the nasal bone is determined by visualization during the procedure of ultrasound in 12 weeks of bearing the fetus. Its absence at this time or a deviation from the generally accepted standards later indicates an incorrect intrauterine development of the child, moreover, it can signal the presence of Down's syndrome in the baby. In such situations, it is recommended to conduct an additional examination.

Some experts, knowing the norms of the first screening, use comparative tabulated values, comparing their values with the results of ultrasound. And again, we should not forget that the very fact of the presence of the fetal nasal bones is of prime importance during the period of 10-12 weeks of pregnancy, and the measurements are not so significant, because the chromosomal anomalies of ossification occur later.

Parameters of the nasal bone in different stages of pregnancy

Individual periods of development and growth of the fetus are characterized by certain regularities. One of the main parameters is the length of the nasal bone. The norm of the nasal bone at 12 weeks is about three millimeters in length. Later, by the 21st week this value reaches 5-5.7 millimeters, and by the 35th week - 9 millimeters.

The accuracy of measurements of an ultrasound of an embryo depends not only on the perfection of the equipment, but also on the experience and professionalism of the specialist.

Table of the main parameters of the nasal bone

The norm of the nasal bone in 12 weeks of fetal development, as well as in the subsequent months of pregnancy of a woman, is systematized and serves as a starting point in the study of ultrasound results. Based on the information received, doctors monitor the entire course of the intrauterine stay of the baby and identify the presence or absence of anomalies.

If the nose bone is not visualized, and the collar part is thickened, then the probability of birth of an infant with Down syndrome or birth defects is extremely high. Knowing this, many parents prefer abortion. Since the birth of a healthy child is not only a task for mothers, but also for doctors, such an indicator as the norm of the nasal bone in 12 weeks is so important. The table below gives a graphic description of its increase during the course of pregnancy.

What determines the length of the nasal bones of the fetus?

After the tenth week of gestation, you can make measurements of the most important characteristics of the fetus. The norm of the nasal bone in 12 weeks should correspond to the required parameters, otherwise one will have to think about the possible severe chromosomal problems of the unborn child. Hypoplasia is considered a symptom of such complex diseases as Down syndrome, Edwards syndrome, Patau, Turner syndrome, etc.

To obtain a more accurate result, an expert ultrasound examination of the fetus is appointed, and with repeated confirmation that the norm of the nasal bone does not correspond to the required values, a genetic analysis of the amniotic fluid is performed. This will allow an objective assessment of the in utero state of the baby, since it is in this environment that oxygen, carbon dioxide, hormones, fetal metabolism products, enzymes accumulate.

Accuracy of modern diagnostics

Convinced from the results of ultrasound diagnosis that the parameters of the nasal bone of a future child are less than normal, the parents succumb to endless despair. It is not worth reacting that way, because one of these parameters is not enough to diagnose Down's syndrome or other serious pathological condition. And although the norms of the first screening are to some extent indicative, one should calmly wait for the repeated results of a deeper examination.

Still it is necessary to understand that every child during the period of intrauterine development is individual, therefore the sizes of separate parts of the body will differ, including the nasal bone in 12 weeks. But if the study of the fetus demonstrates obvious defects of internal organs and shortening of limbs, then in these cases it is possible to speak with confidence about congenital malformations.

What is perinatal screening?

Perinatal screening is a unique examination of a future mother for the detection of the danger of congenital and acquired pathological conditions of fetal development, the results of which are compared with the averaged values.

In the first trimester of pregnancy (10-12 weeks), perinatal screening makes it possible to recognize early enough anomalies in the number of chromosomes, the defect of the anterior abdominal wall and the pathology of the neural tube, as well as various threats to normal childbearing in general.

Based on the rates of RAPP and hCG, characterizing pregnancy, as well as the value of the thickness of the collar space in the embryo, judge the risk of possible defects. If the norms of the first screening do not coincide with those of the analyzes performed, the pregnant woman is assigned a study of the genetics of the unborn child and a biopsy of the villus of the chorion.

What is hypoplasia of nose bones in a fetus

The norm of the nasal bone at 12 weeks during the ultrasound examination suggests a good, healthy fetal development in the early stages of pregnancy. If its length deviates from the adopted standard in the direction of decrease, then hypoplasia of the nasal bone is present. But there are exceptional cases when a number of surveys do not reveal it at all. Then the question is raised about aplasia of the nasal bone, in other words, the complete absence of the organ.

Why do such violations occur?

In fact, the causes of pathological abnormalities from the normal parameters of the length of the paired bones of the nose of the fetus are numerous, and they all have a different character. This can be, for example, chronic alcoholism of one of the parents or severe consequences of smoking. In the risk group, women who have had influenza, colds and other diseases automatically fall into the first trimester of pregnancy.

There are other reasons that the norm of the nasal bone in 12 weeks of fetal development does not reach, namely:

• Taking antibiotics and other strong medications;
• Gamma irradiation;
• Impact on the body of a woman harmful environmental factors;
• Bruises;
• Prolonged overheating of a pregnant woman.

Thus, in addition to chromosomal abnormalities and so-called genetic predispositions, the way of life and health of the future mother directly affects the fetal development of her fetus. And modern medicine, thanks to the latest diagnostic methods, allows to detect and control chromosomal abnormalities in a baby early enough to cause Down's disease. In any case, it is the attending physician, on the basis of the most accurate analyzes and studies, capable of determining the true diagnosis or eliminating possible risks.