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Visualization of the nasal bone at 12 weeks. Fetal nasal bone: normal

The achievements of modern medicine make it possible to carefully monitor pregnant women and identify those who are at risk for possible fetal chromosomal abnormalities. Thus, ultrasound examination of the nasal bone (NK) of the fetus is an important diagnostic tool for identifying a possible anomaly.

The nose is a quadrangular elongated bone. Hypoplasia (or shortening) indicates the underdevelopment of the organ from the very beginning of its formation. Any manifestation of it is a pathology.

Why is it necessary to measure the nasal bone of the fetus?

The length of the nose bone is an indicator of the normal development of the fetus. There are two pathological conditions - hypoplasia and aplasia. Hypoplasia is a decrease in its length, and aplasia is the absence of this bone. Both of these conditions indicate the presence of pathologies in the fetus associated with chromosomal disorders. Identification of this indicator occurs through ultrasound. Its normal values indicate intrauterine development without deviations.

If it is clear that the indicators are small, i.e. there are downward deviations, then this condition is a sign of hypoplasia. An obvious pathology and deviation is the absence of bones, which indicates the absolute underdevelopment of this organ and a gross anomaly. This happens rarely, in exceptional cases.

The nasal bone is visualized by ultrasound already for a period of 10-11 weeks. Deviations in this indicator are considered a sign of some diseases caused by chromosomal disorders. These are conditions such as Down syndrome, Edwards syndrome, Patau syndrome, etc.

In early pregnancy, the presence of this bone in the fetus is important, and measurement of its size for diagnostic purposes should be carried out no earlier than 12-13 weeks. With hyperplasia or aplasia, detected by ultrasound, one can suspect not only abnormal intrauterine development, but also Down syndrome. In this case, it is necessary to conduct an additional examination after 2 weeks to control the situation.

At 10-11 weeks, the doctor checks for the presence of a nasal bone in the fetus, and by 12-13 weeks, deviations in its development can be detected. They indirectly indicate chromosomal abnormalities. The study is carried out by comparing the obtained data with normal indicators

In addition, in such a situation, specialists compare the results of the first screening with the existing standards according to a special table. When deciphering, it should be remembered that, first of all, the fact that the fetus has a nose bone is important, and the measurement indicators at this time are not so informative, since chromosomal abnormalities for this marker appear somewhat later. However, one should not forget that the conclusion about chromosomal abnormalities that entail the birth of a child with serious illnesses is a serious diagnosis that needs careful verification and detailed analysis.

Norms of indicators at different stages of pregnancy

The growth and development of the fetus occurs in accordance with certain patterns and standards, confirmed by science and life. This also applies to the parameters of the nose of the unborn child:

so, the length of 3 mm is considered the norm at 12 weeks;
at 20 weeks, the bone should be from 5.7 to 8.3 mm;
at 35 weeks - at least 9 mm.

How accurately this indicator will be determined depends on the equipment of the ultrasound machine and on the professionalism and qualifications of the doctor conducting such a diagnosis. These norm indicators are the starting point for deciphering and studying the results of prenatal screening.

The information obtained during the examination is the basis for further monitoring of the condition of the fetus in order to identify possible developmental anomalies. If during an ultrasound examination it is impossible to determine the presence of NK and at the same time there is a thickening of the collar zone, then doctors state a high degree of probability that the child will be born with birth defects or with Down's disease.

If the doctor detects bone hypoplasia or cannot find signs of their presence at all, additional studies are carried out. For example, when a thickening of the collar zone is detected, it is possible to diagnose the development of Down syndrome with a high probability.

Determining this parameter is so important that some parents, having learned about this possibility, decide to terminate the pregnancy. Therefore, it is important to undergo appropriate research in a timely manner and make sure that the unborn baby is healthy and does not have various developmental disorders. The presence or absence of hypoplasia indicates the normal or pathological intrauterine development of the child. Only an appropriate specialist can make a diagnosis and determine the likelihood of such a risk.

To determine hypoplasia, the following table is used, which presents the norms of the indicator at various stages of pregnancy. Based on this table, which shows the average, minimum and maximum values, doctors summarize the data obtained on ultrasound and give the appropriate conclusions:

Deadline, week	Average, mm	Minimum value, mm	Maximum value, mm
12 - 13	3,1	2	4,2
14 - 15	3,8	2,9	4,7
16 - 17	5,4	3,6	7,2
18 - 19	6,6	5,2	8
20 - 21	7	5,7	8,3
22 - 23	7,6	6	9,2
24 - 25	8,5	6,9	10,1
26 - 27	9,4	7,5	11,3
28 - 29	10,9	8,4	13,4
30 - 31	11,2	8,7	13,7
32 - 33	11,4	8,9	13,9
34 - 35	12,3	9	15,6

What are the causes of this pathology?

Expectant mothers may have a legitimate question as to what causes such a pathology, and how it is related to the definition of genetic anomalies and defects.

If earlier the fact of the presence of hypoplasia did not attract the attention of doctors, then relatively recently scientific studies have revealed the relationship of such an anatomical deviation with the possibility of having a child suffering from Down syndrome and other chromosomal abnormalities.

As a result of numerous studies in this area, it turned out that such hypoplasia was found in 80% of children born with Down syndrome. This gave grounds for the conclusion that such a pathology, detected by ultrasound, is a sign of congenital abnormalities in the child. Factors that can cause such a deviation are quite diverse. Scientists of genetics distinguish the following of them:

taking strong medications in early pregnancy, including antibacterial drugs;
excessive use of alcohol and tobacco products;
prolonged overheating of a pregnant woman;
hereditary predisposition;
severe illness at an early stage of pregnancy;
infectious diseases such as rubella, toxoplasmosis, influenza, etc.;
injuries and bruises of a pregnant woman;
poisoning with hazardous chemicals;
gamma radiation of a woman during pregnancy;
environmental factors that adversely affect the body of a pregnant woman.

During pregnancy, smoking or even breathing other people's tobacco smoke can be one of the main causes of birth defects in the fetus.

So, such a congenital pathology can be the result of not only a hereditary predisposition, but also appear as a result of maintaining an incorrect lifestyle and the influence of adverse factors, which most often pregnant women do not pay due attention to. However, these factors directly affect the development of the unborn child. Diagnostic methods of modern medicine used in obstetrics make it possible to detect such deviations already in the early stages of pregnancy and inform parents about them.

Diagnosis of hypoplasia

At 10 weeks gestation, ultrasound can be performed to measure various parameters of the fetus that characterize its development. The discrepancy between their indicators of the norm is the basis for making an assumption about possible deviations in development.

If the doctor gives a conclusion about possible hypoplasia, then to clarify this diagnosis, the pregnant woman must undergo an additional study. In the case of its repeated confirmation by ultrasound, amniocentesis is performed - an analysis of amniotic fluid for the presence of genetic abnormalities.

The study will provide objective data on intrauterine development and assess the degree of presence of chromosomal abnormalities. However, even if the ultrasound showed a small, abnormal nose, do not despair ahead of time. This parameter alone is not always enough to issue a conclusion about the presence of a disease and severe pathology. Despite the fact that the indicators of the first screening are of great diagnostic value, it is necessary to conduct a deeper examination and wait for its results.

When diagnosing pathologies, one should not forget about the individuality of any organism, which is characteristic even at the level of intrauterine development. Due to such features, when measuring important indicators, in this case, the nasal bone, they may differ slightly from the given standard values. Therefore, with a high degree of confidence, it is advisable to say that there are chromosomal abnormalities only in the presence of general fetal hypoplasia.

In this case, reduced sizes of all limbs and organs are noted. All this suggests that the difference between the indicators and the accepted norm is not always a sign of one or another malformation. This can only be an individual feature of the unborn child, and he will be born a completely healthy baby. Only a doctor is able to correctly decipher the results of the examination and make a diagnosis.

The task of prenatal screening is to identify pregnant women at high risk for giving birth to children with chromosomal diseases and congenital malformations in order to more detailed analysis of the fetus using special methods.

Since the end of the last century, the calculation of individual combined risk has been included in the prenatal screening algorithm, the central place in which is occupied by ultrasound and biochemical screening in the first trimester (11-14 weeks of pregnancy). Computer programs have been created to calculate the risk, taking into account the age, ultrasound marker of the first trimester (collar space thickness - TVP) and blood biochemical markers (β-hCG and PAPP-A) of a pregnant woman.

Over the past 10 years, this system has fully justified itself and has been further developed by adding additional ultrasound markers to the risk calculation (evaluation of the nasal bone, venous duct, tricuspid regurgitation, some marker congenital malformations). Expanding the examination protocol with the evaluation of new ultrasound markers (nasal bone evaluation, ductus venosus and tricuspid valve flow) improves the sensitivity of combined screening by increasing the detection rate and reducing the false positive rate.

However, their assessment requires appropriate in-depth training of the ultrasound doctor and obtaining a certificate of competence to conduct this type of study, since only after gaining access to a specific type of study, the risk calculation program will take these data into account in its calculations.

The advantages of ultrasound at 11-14 weeks, in addition to setting the exact gestational age, are: early diagnosis of many, assessment of markers of chromosomal abnormalities to identify pregnant women at high risk for chromosomal abnormalities in the fetus, with multiple pregnancies it is possible to establish chorionicity at an early stage, which is the most important factor, determining the outcome of multiple pregnancy, the ability to identify women at high risk for the development of preeclampsia in late pregnancy.

The fetus () for screening of the first trimester should be in the range of 45-84 mm. To assess the nasal bone in the first trimester of pregnancy, strict conditions must be observed. This is an adequate magnification (only the head and upper chest should be in the picture), mid-sagittal scan (the echogenic tip of the nose, palatine process of the upper jaw, diencephalon should be visualized), the nose is represented by three "K" (tip of the nose, skin, bone). The skin and bones of the nose are visualized in the form of an "equality" sign, the nose is parallel to the sensor.

Rules such as fetal size, adequate magnification, mid-sagittal scan are identical to those for TST. Thus, when deriving a correct scan for measuring TVP, which is mandatory when performing an ultrasound study at 11-14 weeks of gestation, the assessment of the nasal bone is performed in the same section, without requiring additional images.

If all criteria are met, then three clearly distinguishable lines should be visible at the level of the fetal nose: the upper line represents the skin, from top to bottom, a thicker and more echogenic than the skin nasal bone is visualized. The third line, visualized anterior to the nasal bone and at a higher level than the skin, is the tip of the nose (Fig. 1).

Rice. 1. Normal nasal bone.

A nasal bone is considered normal when it is more echogenic in structure than normal skin and pathological when it is not visible (aplasia) (Fig. 2) or shorter than normal (hypoplasia) (Fig. 3). In the case of the same or lesser echogenicity of the nasal bone than the skin, the nasal bone is considered pathological (Fig. 4).

Rice. 2. Aplasia of the nasal bone.

A) The arrow indicates the echogenic skin of the fetus.

b) The arrow indicates the absence of the nasal bone.

Rice. 3. Hypoplasia of the nasal bone.

A) The nasal bone at 12 weeks and 2 days is 1.4 mm long (less than the lower limit of normal).

b) Nasal bone 2.1 mm at 14 weeks in a fetus with Down syndrome.

Rice. 4. Pathology of the nasal bone

Rice. 4. Decreased echogenicity of the nasal bone.

So, the pathology of the nasal bone is considered:

absence of the nasal bone (aplasia);
change in its length (hypoplasia);
change in its echogenicity.

Considering that many studies of this important marker were carried out on population groups of different composition, data on the frequency of the absence of the nasal bone in different authors differ. So, according to averaged data from multicenter FMF studies at 11-14 weeks, the nasal bone is absent in euploids (in the case of a normal karyotype) from 1 to 2.6% of fetuses, with chromosomal pathologies: in fetuses with trisomy 21 - in 60%, with trisomy 18 - in 50%, in fetuses with trisomy 13 - in 40%.

Numerous studies have been carried out on the measurement and evaluation of the nasal bone at 11-14 weeks of gestation. Some authors propose to evaluate only its presence or absence (+/-). Some works, in addition to assessing the nasal bone, are devoted to its measurement, comparing the length with the normative values for a given period.

The evolution of the development of the assessment of this marker and the opinion of experts on this matter is perhaps one of the most controversial problems that have not been fully resolved in the screening of the first trimester of pregnancy. Most authors consider the assessment of the nasal bone in the first trimester one of the most difficult tasks among all other markers. And this opinion is not without foundation.

Of course, supporters of the theory that for each race (Asians, African Americans, etc.) and populations of peoples (Buryats, Kalmyks, peoples of the North Caucasus) should have their own percentile standards for each KTR are right. However, these studies can only be carried out when multicenter studies with nasal bone measurement are carried out as part of random screening on normal fetuses.

In the Astraia risk calculation program, when evaluating the nasal bone, there are 4 fields: normal, pathology (aplasia / hypoplasia), not clearly visible, could not be assessed, i.e. in order to make a diagnosis of "Hypoplasia of the nasal bone" you need to make sure that it is actually less than the standard values for a given gestational age, and this can only be done by measuring it and comparing it with a known standard.

The method of assessing the nasal bone is only "yes / no", when it is proposed only to see the nasal bone and compare its echogenicity with the skin is very "apparatus-dependent", i.e. is very variable and depends on the technical settings of the ultrasound scanner. When obtaining a "hard" image, typical for some with specific factory presets (settings) for examining the fetus in the first trimester, the echogenicity of the skin will always be comparable, i.e., the same as the echogenicity of the nasal bone. Thus, practical doctors who do not have the opportunity to work on premium class scanners have objective difficulties in assessing this important additional diagnostic marker.

As supporters of the method of measuring the nasal bone at 11-14 weeks, we present data for the Moscow region. The region is heterogeneous in terms of the ethnic composition inhabiting it. In our work, we used the standard values for the length of the nasal bone published by J. Sonek et al. in 2003, taking the value of the 5th percentile as the lower limit of the norm (table).

Table. Standards for the length of the nasal bone (NK) in the period of 11-14 weeks.

The experts of the district offices of the Moscow region assessed not only the presence and absence of the nasal bone, but also its measurement in all pregnant women (about 150,000 examined over 3.5 years of screening). All 31 experts from the Moscow region have a valid FMF certificate of competence for both TVP and nasal bone assessment. The analysis of the detection of pathology (aplasia / hypoplasia) of the nasal bone in fetuses with chromosomal pathology showed that out of 266 cases of Down syndrome detected prenatally in the fetus in the first trimester, the nasal bone was pathological in 248 cases, which is 93.2%.

This high incidence of nasal bone pathology in Down's syndrome is indicative of a well-chosen nasal bone assessment algorithm, which we never intend to give up, obtaining such highly sensitive results, especially when it comes to the diagnosis of Down's syndrome. In cases of detection of other chromosomal anomalies, the incidence of pathology of the nasal bone was comparable to the literature data. With Edwards syndrome, the nasal bone is pathological in 78 fetuses, which is 71%, with Patau syndrome - in 24 (59%) fetuses, with monosomy X - in 24 (42%) cases, with triploidy - in 22 (49%) fetuses.

I would especially like to emphasize that in our study there were 10 pregnant women of Korean nationality who were at risk for chromosomal pathology. In 4 of them, pathology of the nasal bone in the fetus was diagnosed. It could be expected that this is an ethnic feature, however, all these fetuses had a chromosomal pathology (trisomy 21) during prenatal karyotyping. And, conversely, in 6 fetuses with a normal karyotype, both in length and echogenicity of the nasal bone were within the normative values for this period.

Since the absence of the nasal bone in normal fetuses is more characteristic at 11 weeks of gestation than at 13 weeks, the FMF makes a practical recommendation that if at this time (11 - early 12 weeks) the fetus is missing a nasal bone, provided that other markers are normal (ultrasound and biochemical) should not be taken into account when calculating individual risk. In the future, it is recommended to conduct an additional ultrasound examination after one week. In the event that the nasal bone remains pathological, this fact must be taken into account when recalculating the individual risk for chromosomal abnormalities.

Nasal bone evaluation improves the results of combined screening. The frequency of detection of pathology increases from 90 to 93%. The false positive rate decreases from 3.0% to 2.5%.

Thus, our own data allow us to recommend assessing the nasal bone within 11–14 weeks according to two parameters: echogenicity and length, taking its absence, hypoplasia, and decreased echogenicity as a pathology of the nasal bone.

Literature

Baranov V.S., Kuznetsova T.V., Kashcheeva T.K. Modern algorithms and new possibilities of prenatal diagnosis of hereditary and congenital diseases. Guidelines. St. Petersburg, 2013. S. 23-46.
Nicolaides K.H. Screening for fetal aneuploidies at 11-13 weeks//Prenatal diagnosis. 2011, 31:7-15.
Nicolaides K.H. Per. from English. Mikhailova A., Nekrasova E. Ultrasound examination at 11-13+6 weeks of pregnancy. St. Petersburg, 2007. PH "Petropolis", 142 p.
Kagan K.O., Cicero S., Staboulidou I., Wright D., Nicolaides K.H. Fetal nasal bone in screening for trisomies 21, 18 and 13 and Turner syndrome at 11-13 weeks of gestation // Ultrasound Obstet Gynecol. 2009; 33:259-264.
Kagan K.O., Staboulidou I., Cruz J., Wright D., Nicoladides K.H. Two-stage first-trimester screening for trisomy 21 by ultrasound assessment and biochemical testing // Ultrasound Obstet Gynecol. 2010. V. 36. N 5. P. 542-547.
Cicero S., Curcio P., Papageorghiou A., Sonek J., Nicolaides K. Absence of nasal bone in fetuses with trisomy 21 at 11-14 weeks of gestation: an observational study // Lancet 2001; 358:1665-1667.
Sonek J.D., Mckenna D., Webb D., Croom C., Nicolaides K. Nasal bone length throughout gestation: normal ranges based on 3537 fetal ultrasound measurements // Ultrasound in Obstetrics & Gynecology. 2003. V. 21. N 2. P. 152-155.
Kanellopoulos V., Katsetos C., Economides D.L. Examination of fetal nasal bone and repeatability of measurement in early pregnancy // Ultrasound Obstet Gynecol. 2003 Aug;22(2):131-4.
Cicero S., Bindra R., Rembouskos G., Tripsanas C., Nicolaides K.H. Fetal nasal bone length in chromosomally normal and abnormal fetuses at 11-14 weeks of gestation // Matern Fetal Neonatal Med. 2002; 11:400-402.
Keeling J.W., Hansen B.F., Kjaer I. Pattern of malformations in the axial skeleton in human trisomy 21 fetuses // Am J Med Genet. 1997; 68:466-471.

Ultrasound, or Ultrasound- This is a survey method that is widely used during pregnancy at any time. This diagnostic study is relatively simple, highly informative and safe for both mother and child. The main tasks of ultrasound during pregnancy are:

The following tables provide data on fetal biometrics, which are measured at each. They are presented in the 10th, 50th and 95th percentiles. Most often, they are guided by the 50th percentile, and the rest are considered normal fluctuations.

Dimensions of the fetal head by week of pregnancy

Pregnancy period, weeks	Fronto-occipital size (LZR), mm	Biparietal size (BPR), mm

Circumference of the abdomen and fetal head

Pregnancy period, weeks	Abdominal circumference, mm	Head circumference, mm

The length of the bones of the lower leg and femur of the fetus

Pregnancy period, weeks	Lower leg bones, mm	Femur, mm

The length of the humerus and bones of the forearms of the fetus

Pregnancy period, weeks	Forearm bone length, mm	Humerus length, mm

Norms at the first ultrasound at 10-14 weeks

The first screening ultrasound is performed for a period of 10-14 weeks. Its main tasks are:

The study of the thickness of the collar zone(the area between the soft tissues covering the spine and the inner surface of the skin, filled with fluid). Evaluation of the size of the neck crease is very important, because. is a fairly accurate way of timely diagnosis of various chromosomal diseases, in particular Down syndrome. In the presence of an enlarged collar space, the doctor should refer the pregnant woman for a consultation with a geneticist. A woman is assigned additional examination methods: a blood test for alpha-fetoprotein and chorionic gonadotropin, invasive diagnostic methods (amniocentesis - the study of amniotic fluid, placentocentesis - the study of placental cells, cordocentesis - the study of blood taken from the umbilical cord of the fetus).

Normal values of the collar space (NTP) in the first trimester of pregnancy

Pregnancy period, weeks	Collar space thickness, mm
	percentile	50th percentile	95th percentile
10 weeks 0 days - 10 weeks 6 days
11 weeks 0 days - 11 weeks 6 days
12 weeks 0 days – 12 weeks 6 days
13 weeks 0 days - 13 weeks 6 days

Measurement of the coccygeal-parietal size (KTR). This is an important indicator by which you can determine the size of the fetus and the approximate gestational age.

Values of the coccygeal-parietal size by gestational age

Pregnancy period, weeks	KTR percentile values, mm


10 weeks 1 day
10 weeks 2 days
10 weeks 3 days
10 weeks 4 days
10 weeks 5 days
10 weeks 6 days

11 weeks 1 day
11 weeks 2 days
11 weeks 3 days
11 weeks 4 days
11 weeks 5 days
11 weeks 6 days

12 weeks 1 day
12 weeks 2 days
12 weeks 3 days
12 weeks 4 days
12 weeks 5 days
12 weeks 6 days

13 weeks 1 day
13 weeks 2 days
13 weeks 3 days
13 weeks 4 days
13 weeks 5 days
13 weeks 6 days

Normal heart contractions should occur at regular intervals, i.e. be rhythmic. Arrhythmia may indicate the presence of congenital heart disease or fetal hypoxia. The heartbeat should sound very clear and distinct; in the presence of deaf tones, intrauterine oxygen deficiency can be suspected. An important indicator is the heart rate.

Normal heart rate by gestational age

Tachycardia is an increase in the number of heartbeats more than normal, bradycardia is a decrease in heart rate to 120 beats per minute or less. Most often, such changes in the heartbeat occur during fetal hypoxia as a reaction to a decrease in oxygen in the blood. In such cases, the pregnant woman must be prescribed treatment, which is often carried out in a hospital. A therapy is prescribed aimed at improving uteroplacental blood flow, improving intracellular metabolism.

Evaluation of the development and presence of various organs(bladder, kidneys, liver, stomach, heart), spine, and upper and lower extremities of the fetus. If anomalies in the development of organs are detected, a woman is sent to a genetic consultation. After a detailed examination, a geneticist decides on the viability of the child and the possible termination of pregnancy.

Normal second ultrasound at 20-24 weeks

The doctor prescribes the second planned ultrasound at 20-24 weeks. At this time, the following are investigated:

Biometric indicators(biparietal size, fronto-occipital size, length of tubular bones, abdominal and head circumference). These indicators are measured to assess the growth of the fetus and its appropriate size for the gestational age.
Identification of various fetal malformations. It is in this period that the diagnosis will be the most informative, because. at the first examination, the child is still too small, and at the third planned ultrasound it will already be too large, in addition, the placenta may interfere with a thorough examination if it is located on the anterior wall of the uterus.
Structure, thickness, location and maturity of the placenta. This is the most important organ that supplies the fetus with all the nutrients necessary for its normal development.

Normal thickness of the placenta depending on the gestational age

Pregnancy period, weeks	Permissible fluctuations	Normal values, mm

With an increase in the thickness of the placenta, the doctor may assume the presence (inflammation of the placenta). Making such a diagnosis requires an additional examination for the presence of infection and subsequent treatment in a hospital.

Ultrasound also evaluates maturity of the placenta. This is an important indicator that characterizes the ability of the "children's place" (synonymous with the term "placenta") to provide the fetus with the necessary substances.

Degrees of maturity of the placenta

Late maturation of the placenta is quite rare and is mainly caused by:

smoking mother,
She has various chronic diseases.

Premature maturation of the placenta occurs more frequently. The reasons for this condition are:

Endocrine diseases of the mother (in particular, diabetes mellitus),

If it is located below and overlaps the internal os of the uterus, they talk about. This is a serious type of obstetric pathology that threatens the life and health of a woman and a child. Often this anomaly occurs in multiparous women, after inflammatory diseases of the uterus, uterine myoma, after abortions. A pregnant woman is carefully observed in a hospital or at home, where she must observe complete rest and refrain from sexual activity. In the event of bleeding, immediate hospitalization is required.

Quantity and quality of amniotic fluid

Mean Normal Amniotic Fluid Index

Pregnancy period, weeks	Possible fluctuations	Average

When the amount of amniotic fluid changes in one direction or another, they speak of polyhydramnios and oligohydramnios.

It often occurs in women with infectious diseases, diabetes mellitus, with some fetal malformations, Rh sensitization (incompatibility of the blood of the mother and fetus according to the Rh factor). The condition requires mandatory treatment: antibiotic therapy, drugs that improve uteroplacental blood flow.

- this is a pathological decrease in the amount of amniotic fluid less than 500 ml. The causes of this condition are still unknown. If there is very little water, this may indicate a severe malformation of the fetus: the complete absence of kidneys. There is practically no treatment for oligohydramnios, all therapy is aimed at supporting the child.

The ultrasound specialist also evaluates amniotic fluid quality. Normally, they should be transparent. If there is turbidity, mucus, flakes in the amniotic fluid, there is a suspicion of an infectious process. A woman is tested for hidden infections and is being treated.

Cord evaluation. Ultrasound examination can detect the entanglement of the umbilical cord around the cervix of the fetus. But in the second trimester of pregnancy, it does not cause alarm. The baby is in constant motion, and the umbilical cord can unwind.
Grade. Normally, the neck should be at least 3 cm, and only closer to childbirth does it begin to shorten and smooth out. The internal os must be completely closed. Shortening of the neck or opening of the pharynx is a sign. A woman should have her cervix stitched or (a mechanical device in the form of several rings that is inserted into the vagina and protects the cervix from premature opening).

Third ultrasound at 32-34 weeks

The third planned ultrasound is carried out for a period of 32-34 weeks. Its tasks are:

Positioning and. At this time, the child is already quite large and its mobility is limited. The position in which he is during the ultrasound will remain until the end of the birth. The definition of these indicators is important for resolving the issue of the method of delivery. Allocate longitudinal, transverse and oblique position of the fetus. With a longitudinal location of the child, a woman can give birth naturally, the transverse and oblique position are relative indications for surgery. Natural childbirth is also possible with a normal cephalic presentation of the fetus, the pelvic location is an indication for operative delivery.
Assessment of the size and weight of the fetus. These indicators help to understand how the child develops. If the size of the fetus is behind the average, you can suspect a delay in intrauterine development of the child. Determination of fetal malnutrition requires the start of treatment for a pregnant woman. If the fetus, on the contrary, is ahead of the indicators, then we can talk about. Probably the birth of a child with a large weight (more than 4 kg). This can significantly complicate childbirth, so a woman is often offered an operative delivery.
The study of the placenta, its size, degree of maturity and place of attachment. Migration of the placenta in this period has already been completed, it will occupy the same position for childbirth. It should be borne in mind that natures are possible only by caesarean section. With a low location of the child's place, the birth of a child through the natural birth canal is possible, but this is fraught with a high risk of bleeding during childbirth.
Assessment of the quantity and quality of amniotic fluid(See topic: normal values for the second planned ultrasound at 20-24 weeks).

The norm of ultrasound before childbirth

Ultrasound examination before childbirth is not mandatory for all pregnant women and is carried out selectively according to indications. Its main task is to resolve the issue of the method of delivery. During an ultrasound, the following is determined:

Position and presentation of the child;
Estimated fetal weight at birth;
Cord position for exclusion.

More recently, the parameter - the norm of the nasal bone in the fetus - was not thought about. An ultrasound device for examining pregnant women appeared in antenatal clinics only 25 years ago - such an examination was not carried out without fail. Blood-urine general, specific analysis for syphilis, in some cases, the Rh factor was determined.

Now, during an ultrasound examination, it is necessary to measure the length of the nasal bone of the fetus and compare it with the tabular values. By this parameter, it is possible to approximately identify pathologies and the likelihood of chromosomal abnormalities - Turner, Edwards, Down and others.

Examination for the presence of anomalies in development

The nasal bone is an elongated quadrangular bone formation. It is not yet visible at 9-10 weeks, but already at 10-11 weeks, an ultrasound examination should show its presence.

In the future, its increase is compared with the tabular values of the sizes.- a table was specially compiled, which shows the average rate of fetal development by week, its length, dimensions of internal organs, bone formations are given, and among them the parameters of this bone, which is very important for diagnosing.

At 10-11 weeks of pregnancy, it is not possible to measure the bone, but it must already be present. If not, then studies of chromosomal pathologies should be carried out further.

The discrepancy between the tabular sizes indicates that the fetus has hypoplasia of the nasal bone. But this does not mean that the unborn child has 100% Down's disease. The doctor takes into account not only the length of this bone, but also analyzes other parameters, comparing them.

To determine the rate of fetal development, it is necessary to take into account the individual characteristics of the parents of the unborn baby:

height;
Lifestyle;
features of mother's nutrition during pregnancy;
mother's nationality and father's nationality.

In addition, changes are considered in dynamics, given that they can differ by 1-2 mm on different devices, and this bone has very small dimensions.

The final result can be obtained only by passing specific tests.

An ultrasound examination of the fetus gives a 50-80% chance of the disease, so you should not despair.

If a woman has decided to give birth in any case, then further examinations can be omitted. But if she hesitates - and this cannot be condemned in any way, since raising a child with such a pathology can be equated with a feat - then research must be continued.

Research on Down's Syndrome

Doctors immediately warn expectant mothers that the earlier the screening is carried out, the higher the likelihood of a miscarriage after the procedure.

When tests are taken for up to 14 weeks, miscarriages occur in 3% of cases, during relative well-being - from 17 to 22 weeks - in 0.5%. At week 23, the risk of miscarriage rises again and is already 1%.

Chorionic biopsy - placental chorion villi are taken for analysis, without affecting the fetus. The study period is 12-14 weeks of pregnancy.

At 13-18 weeks, placentocentosis is done - during it, the cells of the mature placenta are examined.

Amniocentosis is performed at 17-22 weeks. Amniotic fluid with a chromosome set similar to that of the fetus is collected for analysis with a thin needle that is inserted through the mother's abdomen.

During cordocentesis, blood from the umbilical cord is taken for examination.

The procedure is carried out without anesthesia, a thin needle is also inserted through the abdomen and uterine wall, as in amniocentosis, only other biological material is taken for examination.

All actions are controlled on the screen of the ultrasound machine, this reduces the risk of causing damage to the fetus.

After carrying out specific tests, it is advisable for a woman to spend several days in the hospital to stabilize the condition and stop the tone of the uterus.

Many future mothers refuse such studies, they think the price is high - the possibility of a miscarriage if it turns out that the child is developing normally. But as mentioned above, ultrasound research has a low probability of accurate diagnosis.

Specific changes are as follows:

Week 10 - the nasal bone should be visible during ultrasound examination;
12-13 weeks - 3 mm;
at 14-15 weeks of fetal development - 3.4 - 3.6 mm;
18-19 - 5 - 5.2 mm;
20-21 - 5.2 - 5.7 mm;
22-23 - 5.8 - 6.1 mm;
at 24-25 weeks of fetal development - 6.5 - 6.9 mm;
26-27 - 7.2 - 7.6 mm;
28 -29 - 8.1 - 8.5 mm;
at 30-31 weeks of fetal development - 8.6 - 8.7 mm;
32-33 - 8.9 mm;
at 34-35 weeks - 9 mm.

The measurement error depends on the qualifications of the doctor who conducts them. The human factor in evaluating the results should also be taken into account.

Correction of fetal development

Sometimes the nasal bone and other parameters differ from the norm not because of chromosomal abnormalities, but because of external factors that inhibit the development of the fetus. Correction of fetal development.

In this case, the pregnant woman is advised:

streamline food
switch to a diet that contains enough nutrients for the development of the fetus;
completely abandon bad habits;
engage in physical therapy;
take special drugs prescribed by the doctor after assessing the clinical picture - a study of the development of the fetus and placenta.

Quite often, infections are the cause of fetal hypotrophy.

The length of the nasal bone in the embryo is one of the most important indicators of the proper development of the fetus. If the nasal bone on ultrasound is smaller than normal, we can talk about such a phenomenon as hypoplasia of the nasal bone in the fetus.

Hypoplasia of the nasal bone is a marker of a chromosomal disorder and abnormal development of the fetus, but this is not yet a diagnosis. By itself, hypoplasia does not make it possible to say with a high degree of accuracy about the genetic disorders of the embryo, but it allows timely conduct of more informative studies than ultrasound.

According to statistics, prenatal diagnosis has reduced the frequency of birth of children with Down syndrome, Patau, Edwards and other chromosomal diseases by one and a half times.

Purpose of measuring the nasal bone in the fetus

The relationship between the size of the bony part of the nose and the physical development of the embryo was revealed by scientists recently. Therefore, the determination of the length of the nasal bone on ultrasound as part of the plan for mandatory diagnostics during pregnancy began to be carried out only a few years ago. After doctors reported that children with nasal hypoplasia were born with Down syndrome approximately 80 times more often than embryos whose nasal bone met the standards.

The advantage of ultrasound to detect such a factor as nasal bone hypoplasia over more informative studies is its safety and painlessness. Determination of the size of the nose bone is performed during a routine screening. The results can be obtained immediately after the procedure, but if the ultrasound shows the underdevelopment of the embryo's nose bone, the procedure will need to be repeated.

The norm of the nasal bone in the fetus by weeks

Hypoplasia of the nose is detected by comparing the length of the nasal bone of the embryo on ultrasound with a similar average value of healthy children. An unequivocal sign of a violation is aplasia - the complete absence of the nasal bone, but a decrease in the length of the bone part of the nose can also only indicate probable pathologies.

Given the fact that the indicator may vary slightly due to individual characteristics (embryo size, exact gestational age), the diagnosis is made if the indicator is below the minimum acceptable threshold.

The table shows the dimensions of the nasal bone by week: it indicates the age of the fetus (week), the corresponding length of the nasal bone to age - the maximum and minimum, as well as the average value, all dimensions in mm.

Embryo age (weeks)	Acceptable range (mm)	Average (mm)
12 - 13 weeks	2,0 – 4,2	3,1
14 - 15 weeks	2,9 – 4,7	3,8
16 - 17 weeks	3,6 – 7,2	5,4
18 - 19 weeks	5,2 – 8,0	6,6
20 - 21 weeks	5,7 – 8,3	7,0
22 - 23 weeks	6,0 – 9,2	7,6
24 - 25 weeks	6,9 – 10,1	8,5
26 - 27 weeks	7,5 – 11,3	9,4
28 - 29 weeks	8,4 – 13,4	10,9
30 – 31 weeks	8,7 – 13,7	11,2
32 - 33 weeks	8,9 – 13,9	11,4
34 - 35 weeks	9,0 – 15,6	12,3

It is important to understand that the accuracy of the study depends on several factors. For example, from the qualifications of the doctor performing the ultrasound, and the equipment on which he works. There is a risk of a false conclusion when conducting any medical research, therefore, in case of a negative result, at least one repeated diagnostic procedure is performed.

Hypoplasia of the nasal bone

Hypoplasia of the NK (nasal bone) on ultrasound is the basis for a series of tests that will refute or confirm developmental abnormalities.

If a small nasal bone is found on ultrasound, do not panic. A thorough examination during pregnancy is a necessity that increases the chances of having a healthy baby, while the stress of intermediate results of the study can harm both the fetus and the pregnant woman herself.

Possible reasons

The main cause of nasal bone hypoplasia is developmental delay caused by genetic defects. That is, the etiology of hypoplasia is best considered as the cause of genetic abnormalities, including Down syndrome.

Toxic effects on the body of the embryo in the early stages. In addition to the obvious sources of poisoning of the body - alcohol, smoking, exposure to adverse environmental conditions, the toxic effect may be due to taking medications. That is why taking any drugs throughout pregnancy can be carried out exclusively under the supervision of the attending physician. Toxic effects can also occur against the background of food poisoning.
The most common cause of genetic abnormalities are infectious diseases suffered by the expectant mother during pregnancy: rubella, influenza. By themselves, these diseases are not dangerous, but the virus enters the fetus through the blood. The embryo cannot cope with the infection, so the virus causes developmental disorders. This does not always happen, the frequency of cases of damage to the body of the fetus when the mother is infected depends on the duration of pregnancy. In the first weeks of pregnancy, the probability of pathology is about 80%, and after 13 weeks it decreases to 10%. Even a ten percent risk of infection of the embryo makes one consider viral diseases of a pregnant woman a dangerous phenomenon that threatens to result in stillbirth, miscarriage, and developmental deviations.
Unfavorable external conditions can lead to disruption of the process of normal embryonic development. For example, the physical trauma received by the expectant mother or heat stroke. External factors that can lead to a slowdown in the development of the fetus and, as a result, a decrease in the nasal bone, include the effects of gamma radiation.
An important aspect in the matter of proper development is the hereditary factor. With unfavorable heredity, the risk that the fetus will have an underdevelopment of the nasal bone on ultrasound increases many times over.

In the event that a pregnant woman has undergone one of these factors, she must definitely visit an obstetrician-gynecologist, and also inform the specialist conducting ultrasound screening about this.

Additional diagnostic methods

After the hypoplasia of the nasal bones in the fetus is detected on the monitor of the ultrasound device, the doctor will refer the patient for further examination.

First of all, the doctor conducts a second ultrasound, which measures not only the bones of the nose, but also other organs. If the development of the embryo, with the exception of the length of the nasal bone, corresponds to its age, the risk of a genetic anomaly is minimal. In some cases, repeated ultrasound shows that the first result was false.
The most accurate method for detecting genetic abnormalities of the fetus is amniocentesis.

How is an amniocentesis performed?

The study is a sampling of amniotic fluid from the embryonic membrane. It contains fetal cells, which are the material for analysis. Amniotic fluid is used for a number of tests:

hormonal;
immunological;
biochemical;
clinical.

But to identify the pathology of the development of the embryo, a cytological study is carried out.

The process of performing amniocentesis under ultrasound guidance.

The fluid is taken with a thin needle, the movements of which are controlled by an ultrasound sensor.
As a rule, anesthesia is not required during the procedure, but if the pregnant patient wishes, the doctor can anesthetize the area where the needle is inserted.
The amniocentesis process lasts no more than one and a half minutes, after which the patient is invited to spend a couple of hours in the ward under the supervision of medical personnel.

The study is considered safe, but before conducting it, it is required to collect the patient's history in order to exclude complications, for example, bleeding with reduced blood clotting.

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