Modern medicine has achieved tremendous success in examining pregnant women, and if earlier it was considered quite sufficient to undergo an ultrasound examination of the fetus and pass some tests, then today this category of patients is under the watchful eye of specialists and is subjected to periodic procedures and examinations. Basically, they are aimed at determining the condition of the baby developing in the womb of the mother and timely diagnosis of various anomalies. Including ultrasound detection of such a characteristic as the norm of the nasal bone, carried out after ten weeks of pregnancy.
The need to measure the nasal bone of the fetus
A paired, quadrangular nasal bone is determined during imaging during an ultrasound procedure at 12 weeks of gestation. Her absence at this time or deviation from generally accepted standards later indicates improper intrauterine development of a child, moreover, it can signal the presence of Down syndrome in the baby. In such situations, the mandatory conduct of an additional examination is recommended.
Some specialists, knowing the norms of the first screening, use comparative tabular values, comparing their values with the results of ultrasound. And again, one should not forget that the fact of the presence of the nasal bone of the fetus is of primary importance during the period of 10-12 weeks of pregnancy, and the measurements are not so indicative, because chromosomal ossification ossifications occur later.
Parameters of the nasal bone at different stages of pregnancy
Certain periods of development and growth of the fetus are characterized by certain laws. 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 ultrasound measurements of the 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 at 12 weeks of fetal development, as in the subsequent months of pregnancy of a woman, is systematized and serves as a starting point for studying the results of an ultrasound study. 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 nasal bone is not visualized and the collar part is thickened, then the probability of having a baby with Down syndrome or congenital defects of the face is extremely high. Knowing this, many parents prefer abortion. Since the birth of a healthy child is a task not only for mothers, but also for doctors, such an important role is assigned to such an indicator as the norm of the nasal bone at 12 weeks. The table below gives a clear description of its increase during pregnancy.
Norm of the nasal boneTerm weeks | Minimum value, mm | Maximum value, mm |
| 12-13 | 2.0 | 4.2 |
| 14-15 | 2.9 | 4.7 |
| 20-21 | 5.7 | 8.3 |
| 22-23 | 6.0 | 9.2 |
| 32-33 | 8.9 | 13.9 |
| 34-35 | 9.0 | 15.6 |
What gives a determination of the length of the nasal bone of the fetus?
After the tenth week of gestation, you can take measurements of the most important characteristics of the fetus. The norm of the nasal bone at 12 weeks should correspond to the required parameters, otherwise you will have to think about possible severe chromosomal problems of the unborn child. Hypoplasia is considered a symptom of complex diseases such as Down, Edwards, Patau, Turner, and others.
To obtain a more accurate result, an expert ultrasound examination of the fetus is prescribed, and with repeated confirmation that the norm of the nasal bone does not correspond to the necessary values, a genetic analysis of amniotic fluid is performed. This will make it possible to objectively assess the intrauterine condition of the baby, since it is in this environment that oxygen, carbon dioxide, hormones, fetal metabolic products, and enzymes accumulate.
The accuracy of modern diagnostics
Having made sure from the results of ultrasound diagnostics that the indices of the nasal bone of the unborn child are less than normal, parents succumb to endless despair. You should not react like that, because this parameter alone is not enough to diagnose Down syndrome or another serious pathological condition. Although the norms of the first screening are to some extent indicative, you need to calmly wait for the repeated results of a deeper examination.
It must also be understood that each child during the period of intrauterine development is individual, because the sizes of the individual parts of the body will differ, including the nasal bone at 12 weeks. But if the study of the fetus shows obvious defects in the internal organs and shortening of the limbs, then in these cases we can confidently talk about congenital malformations.
What is perinatal screening?
Perinatal screening is a unique examination of the expectant mother to detect the danger of congenital and acquired pathological conditions of fetal development, the results of which are compared with averaged values.
In the first trimester of pregnancy (10-12 weeks), perinatal screening allows early recognition of abnormalities in the number of chromosomes, a defect in the anterior abdominal wall and pathology of the neural tube, as well as various threats to the normal bearing of the baby in general.
Based on the PAPP and hCG indicators characterizing pregnancy, as well as the value of the thickness of the collar space in the embryo, the risk of possible defects is judged. If the norms of the first screening do not coincide with the indicators of the tests, the pregnant woman is prescribed a study of the genetics of the unborn child and a biopsy of the chorionic villi.
What is fetal nasal hypoplasia
The norm of the nasal bone at 12 weeks during an ultrasound scan allows us to conclude that the fetus is developing well in the early stages of pregnancy. If its length deviates from the accepted standard in the direction of reduction, then there is hypoplasia of the nasal bone. But there are exceptional cases when a number of surveys conducted do not reveal it at all. Then the question is raised about aplasia of the nose bone, in other words, the complete absence of an organ.
Why do such violations occur?
In fact, there are many causes of pathological deviations from normal indicators of the length of the paired bone of the nose of the fetus, and all of them are of a different nature. This may be, for example, chronic alcoholism of one of the parents or severe consequences of smoking. Women who have had the flu, colds and other diseases in the first trimester of pregnancy automatically fall into the risk group.
There are other reasons that the norm of the nasal bone at 12 weeks of fetal development does not get, namely:
- taking antibiotics and other strong medications;
- exposure to gamma radiation;
- the impact on the body of a woman of harmful environmental factors;
- bruises;
- prolonged overheating of a pregnant woman.
Thus, in addition to chromosomal abnormalities and the so-called genetic predispositions, the lifestyle and health of the expectant mother directly affect the intrauterine development of her fetus. And modern medicine, thanks to the latest diagnostic methods, allows early enough pregnancy to identify and control chromosomal abnormalities in the baby, the result of which may be Down's disease. In any case, it is the attending physician, based on the most accurate analyzes and studies, who is able to determine the true diagnosis or eliminate possible risks.