What is the fetal collar zone? What is the nuchal space in the fetus and what does its enlargement indicate? Consequences of thickening of the collar area

Chelyabinsk State Medical Academy

The problem of hereditary and congenital pathology, primarily congenital malformations (CDM), chromosomal and monogenic diseases, has acquired serious socio-medical significance over the past decade. The frequency of congenital and hereditary pathologies in the population averages 5% of the number of newborn children. In the structure of perinatal morbidity and mortality, congenital and hereditary pathologies occupy 2-3 places. The widespread introduction of screening ultrasound into clinical practice at 11-14 weeks of pregnancy allows for early prenatal diagnosis of congenital malformations and chromosomal abnormalities (CA). Among the numerous echographic markers of CA, the thickness of the nuchal translucency is considered the most valuable. The use of this marker makes it possible to detect up to 66.7-92% of chromosomal defects already in the early stages of pregnancy. Therefore, it is of scientific interest to further study the increase in the thickness of the nuchal space (TN) of the fetus as a prenatal echographic marker of congenital and hereditary pathology.

The purpose of the study was an assessment of the thickness of the fetal nuchal space as a marker of chromosomal abnormalities and congenital malformations of the fetus.

Material and methods. Type of study: cohort with a prospective cohort (2008 - 2010).

Sampling method: continuous as accessed.

Inclusion criteria:

1. Pregnancy at 11-14 weeks gestation.

2. Known date of the last menstruation with a 26-30 day cycle.

3. The woman’s consent to participate in the study.

Exclusion criteria:

1. Menstrual irregularities.

2. Instructions to take hormonal contraceptives two months before the conception cycle.

3. Stimulated pregnancy.

4. Multiple pregnancy.

In accordance with the inclusion/exclusion criteria for the specified period, 1310 pregnant women with a gestation period of 11 to 14 weeks were selected, who were registered at antenatal clinics in Chelyabinsk.

After ultrasound screening, pregnant women were divided into two groups, taking into account the size of the thickness of the nuchal space (TN) of the fetus: the main group - 175 women with an increase in the size of the thickness of the nuchal space in the fetus (group 1), the comparison group - 1135 patients with normal sizes of the thickness of the nuchal space spaces in the fetus, whose pregnancy ended in timely labor and the birth of normal healthy children (group 2). 95‰ TVP from the indicators developed as a result of our research, according to the recommendations of N.A., was taken as threshold (dividing) values. Altynnik and M.V. Medvedev and K. Nicolaides et al. . The groups were comparable by age, parity and gestational age.

Ultrasound examinations were carried out using ultrasonic scanners from TOSHIBA (Japan) of high (XARIO XG) and expert (APLIO XG) classes. To measure the size of the TVP, a transabdominal scanning approach was used. In cases of registration of echographic markers of chromosomal defects or congenital malformations in the fetus, the study was completed with transvaginal access for a detailed study of the anatomy and conducting extended echocardiography of the fetus. During prenatal counseling, the patient was informed about the risk of chromosomal pathology and the advisability of prenatal karyotyping was explained. At 11-13 weeks of gestation, transabdominal chorionic villus aspiration was performed. If prenatal karyotyping is rejected in the early stages and other echographic markers of chromosomal pathology or congenital malformations of the fetus are identified in the second trimester of pregnancy, it was recommended to assess the fetal karyotype by cordocentesis at 21-24 weeks.

Statistical data analysis was carried out using the statistical software package STATISTICA 6.0 (StatSoft, 2001) and MedCalc (9.1.0.1) for Windows. When the distribution of the characteristic in the sample was close to normal, the quantitative values ​​were presented in the form of the arithmetic mean and its standard deviation (M±σ).

To assess the differences between the two groups in quantitative characteristics, taking into account the nature of the distribution, which is close to normal, the Student t-test was used. Assessment of intergroup differences in qualitative characteristics was carried out using the χ 2 criterion, and for expected frequencies less than 10, the Yates correction was applied.

In order to assess the prognostic significance of the indicators, ROC analysis was carried out to calculate sensitivity, specificity, positive and negative likelihood ratios. For all analyses, p values ​​were considered statistically significant.<0,05.

Research results. The age of pregnant women varied from 16 to 45 years. The average age of the patients in the groups was comparable: in group 1 - 28.7±5.43 years, in group 2 - 29.0±6.10 years (p>0.05).

According to our data, the thickness of the nuchal space of the fetus in group 2 (with timely delivery and the birth of a healthy child) gradually increases from 11 to 14 weeks, averaging 1.3±0.3 mm at 11-12 weeks, 1.4 ±0.4 mm at 12-13 weeks and 1.5±0.3 mm at 13-14 weeks, with no differences between the TVP values ​​at these stages of pregnancy (p>0.05).

In table Figure 1 shows the thickness of the fetal nuchal space at 11-14 weeks of pregnancy in the comparison groups.

Note: * - significance of differences (p<0,05) при сравнении групп 1 и 2

In the main group, the numerical values ​​of the expanded nuchal space of the fetus varied from 2.5 to 11.0 mm and exceeded the corresponding indicators (5th, 50th, 95th centile) in the comparison group at 11-12, 12-13 and 13 -14 weeks of pregnancy (Fig. 1).

Of the 175 fetuses in which enlargement of the nuchal space was detected at 11-14 weeks of pregnancy, prenatal or postnatal karyotyping to exclude chromosomal abnormalities was carried out in 160 cases. Of these, chromosomal defects were found in 46/160 (28.8%) cases. In 114/160 women (71.2%) the karyotype was normal. In 15 cases, the chromosome set of the fetus/newborn remained beyond our knowledge due to the patient’s refusal to undergo an invasive diagnostic procedure or due to the lack of a sufficient number of metaphases in the chorionic villus biopsy specimen.

The structure of chromosomal abnormalities is shown in Fig. 2.

Among the diagnosed chromosomal abnormalities, aneuploidy was the most common (78.3%, n=22): Down syndrome was registered in almost every second observation (47.8%, n=22); Edwards syndrome was detected in almost every third case (28.3%, n=13), and Patau syndrome, in our study, was the rarest finding (2.2%, n=1). The proportion of monosomy X (Turner syndrome) was 6.5% (n=3). The proportion of other chromosomal defects was 15.2% (n=7). Among the CA data, the following were recorded: triploidies on the X chromosome (4.3%, n=2), unbalanced translocations (4.3%, n=2), pathological structural changes of chromosomes (2.2%, n=1), marker chromosomes (2.2%, n=1) and sex chromosome aneuploidy syndrome (2.2%, n=1).

The frequency of chromosomal abnormalities varied depending on the thickness of the nuchal translucency, shown in Fig. 3.

Thus, with an increase in the numerical values ​​of TVP, the frequency of chromosomal diseases increased.

In addition, when recording the expansion of the nuchal translucency, in almost every second case (43.2%, n=76), congenital defects were detected: their frequency was higher with an abnormal karyotype, compared with normal - 69.7% (n=53) and 30.3% (n=23), respectively, p<0,001. Структура врожденных пороков развития в основной группе представлена в табл. 2.

When chromosomal abnormalities were detected in the group with TVP expansion, multiple malformations and congenital heart defects were diagnosed more often; gastrointestinal tract, MPS, CNS, CMS and CG neck defects were somewhat less common, compared to those in fetuses/newborns with a normal set of chromosomes. There were no differences in the incidence of other fetal malformations.

Note: NS - p>0.05

Thus, in accordance with the data obtained, it is necessary to classify patients with enlarged TVS in the fetus as a high-risk group for congenital malformations, even in the absence of chromosomal pathology. Particular attention should be paid to a detailed study of fetal anatomy and echocardiographic examination, since multiple congenital malformations and heart defects are most often recorded.

In order to assess the prognostic value of the TVP value in relation to the development of fetal chromosomal abnormalities in the comparison groups, we used ROC analysis (Fig. 4).

The analysis showed that the thickness of the nuchal translucency above 2.6 mm is associated with a high risk of developing chromosomal abnormalities, and this level has high sensitivity (100%) and specificity (89.7%), as well as a positive likelihood ratio (9.65 ), R<0,001.

In recent years, many authors have published information that an increase in TVP can be observed not only with chromosomal pathology in the fetus, but also with various congenital malformations. Most of these defects can potentially only be diagnosed later in pregnancy or even after birth. In order to assess the prognostic value of the TVP value in relation to congenital malformations of the fetus, we also used ROC analysis (Fig. 5). An assessment of the association of TVP with various fetal congenital malformations is presented in Table. 3.

According to the data obtained, a TPV value above 2.6-2.8 mm is associated with almost all congenital malformations, has high sensitivity (100%) and specificity (87% and higher), which is advisable to use in clinical practice.

conclusions

1. In the group of pregnant women, with an increase in the thickness of the fetal nuchal space, chromosomal abnormalities and congenital malformations are more common.

2. Nuchal translucency thickness above 2.6 mm is associated with a high risk of developing chromosomal abnormalities (sensitivity - 100%, specificity - 89.7%, positive likelihood ratio - 9.65, p<0,001).

3. The thickness of the nuchal translucency above 2.6-2.8 mm is associated with almost all congenital defects of the fetus (multiple congenital defects, congenital heart defects, gastrointestinal tract defects, etc.), having high sensitivity (100%) and specificity ( 87% and above).

4. Threshold values ​​of nuchal translucency thickness above 2.6 mm are advisable to use in prenatal diagnosis of congenital fetal pathology.

Notes: * - + LR - positive likelihood ratio; - LR - negative likelihood ratio; AUC - area under the ROC curve

List of sources used:

1. Standard values ​​of the coccygeal-parietal size and thickness of the fetal nuchal space in early pregnancy / N.A. Altynnik, M.V. Medvedev // Ultrasound diagnostics. Obstetrics Gin. Pediatrician. - 2001. - T. 9, No. 1. - P. 38-40.

2. Diagnostic value of the expanded nuchal space in combination with Doppler study of fetal-placental blood flow in the first trimester of pregnancy in congenital and hereditary pathologies / S.G. Ionova, I.P. Tsymbalova, A.V. Sidorova // Prenatal diagnosis. - 2004. - T. 3, No. 3. - P. 233.

3. Kopytova E.I. Enlarged nuchal space of the fetus as a prenatal echographic marker of congenital and hereditary diseases: Abstract of thesis. dis. ...cand. honey. Sci. - M., 2007. - 22 p.

4. Medvedev M.V. Basics of ultrasound examination in obstetrics. - M.: Real Time, 2006. - 96 p.

5. Basics of ultrasound screening in 11-14 weeks of pregnancy / M.V. Medvedev, N.A. Altynnik. - M.: Real Time, 2008. - 88 p.

6. A new approach to calculating risk when conducting screening ultrasound in the first trimester of pregnancy / E.S. Nekrasova, A.L. Koroteev, T.V. Kuznetsova, V.S. Baranov // Prenatal diagnosis. - 2005. - T. 4, No. 1. - pp. 22-28.

7. Multicenter study of first-trimester screening for trisomy 21 in 75 821 pregnancies: results and estimation of the potential impact of individual risk-oriented two-stage first-trimester screening/ K.H. Nicolaides, K. Spencer, K. Avgidou et al. // Ultrasound Obstet. Gynecol. - 2005. - Vol. 25. - P. 221-226.

When carrying out, special attention is paid to thickness of the collar space (TVP), the value of which correlates with the presence fetal chromosomal diseases(first of all, this concerns). Therefore, the determination of TVP, coupled with today, is one of the main criteria for the formation of a risk group for chromosomal pathology. Collar space- this is the area between the inner surface of the skin of the fetal neck and the outer surface of the soft tissues that cover the cervical spine. TVP measurement is carried out at the following mandatory conditions:

• strictly sagittal scanning the fetus/embryo (the sagittal plane goes from front to back and divides the human body into two symmetrical parts);
• gestation period 10-14 weeks with numerical values (KTR) from 45 to 84 mm.

Determination of TVP using ultrasound

During pregnancy, women undergo an ultrasound examination and use it to determine TVP. The procedure is prescribed once per trimester and is aimed at identifying pathologies. To determine them, echographic markers are measured in the fetus. The obtained parameters correspond to the norm. The most important study is in the first trimester, after which the marker data loses relevance.

During the first trimester the following is measured:

• limb length;
• profile bones;
• thickness of the collar space.

To carry out the last of these measurements, the ultrasound specialist uses a sensor to direct a sound wave to the neck area under the back of the head or to the first spine and takes readings. In this place, between the skin and bone tissues of the embryo, subcutaneous fluid accumulates. Its presence may indicate both a normally developing pregnancy and abnormalities in the unborn child. Later, the amount of liquid gradually decreases, and the result of the study loses its information content.

For accurate diagnosis, when measuring the thickness of the collar space, several conditions must be met:

• The pregnant woman is in a lying position;
• The fetus is placed in a convenient position for examination. A lateral position is considered suitable when the profile can be analyzed. If the desired position is not occupied, then a transvaginal examination is performed.
• Coccygeal-parietal size ratio;
• Compliance with diagnostic deadlines;

In addition, the specialist must be competent in the matter of TVP. The apparatus used to carry out diagnostics also plays an important role.

When measuring a collar, two rules are also observed:

• Taking into account the thickness of the amniotic membrane;
• Using Doppler.

Norms for the thickness of the collar space

Medical statistics on the thickness of the nuchal translucency at different stages of pregnancy are presented in the following table.

Important Values ​​exceeding the 95th percentile are taken as deviations from the norm.

The likelihood of developing chromosomal diseases

The likelihood of chromosomal abnormalities is directly proportional to the increase in TVP, and the most common pathologies are:

1. (trisomy 21, more than 50%);
2. (trisomy 18, ?25%);
3. (monosomy on the X chromosome, ?10%);
4. (trisomy 13 chromosome, ?5%), etc.

Trisomy is the presence of an additional chromosome, and monosomy– absence of a chromosome in the chromosome set. Dependence of chromosomal abnormalities on the value of TVP (study P. Pandya) is presented in the table.

If TVP is not normal

At the moment, the optimal way to form a risk group for chromosomal abnormalities is a combined examination, including determination of TVP by , analysis ( β- PAPP-A in the blood serum of a pregnant woman) and. After this, a conclusion is issued, which notes the risk for chromosomal abnormalities (for example, a combined risk of 1:300). If there is a high risk, a woman is recommended to undergo sampling to determine the chromosome set of the fetus. May also be offered cordocentesis(cord blood collection) or chorionic villus biopsy(collection of material from chorionic villi).

Information It should be remembered that these examination methods are carried out only with the informed consent of the pregnant woman, and every woman has the right to refuse them!

With a normal chromosome set (23 pairs of chromosomes), pregnancy is prolonged as usual. If there are severe chromosomal diseases that are incompatible with life, the woman is strongly recommended to terminate the pregnancy. If Down syndrome is present, the family can independently decide on the future fate of the unborn child (prolong the pregnancy or terminate it). Thus, the determination of TVP is fundamental in case of pregnancy, as it makes it possible to timely diagnose the chromosomal pathology of the fetus and make the correct and informed decision about each specific pregnancy.

If the thickness of the collar space is increased

With an increased TVP, a woman is included in the risk group. Depending on other indicators, this will be a medium or high group. The most common abnormalities associated with TVP expansion are chromosomal:

• Down syndrome
• Patau syndrome
• Turner syndrome
• Edwards syndrome.

In addition to the incorrect number of chromosomes, the size of the neck fold can be affected by:

• Heart defects
• Improper lymph circulation
• Anomalies in the development of connective tissues
• Deviations in the formation of bone structures

This may also be due to a complicated pregnancy:

• Anemia
• Taxoplasmosis
• Cytomegalovirus
• Parvovirus.

If the result is unfavorable, the woman is recommended to undergo an ultrasound scan every four weeks to monitor growth or, conversely, a decrease in fluid in the cervical spine. In addition, future mothers who are at risk are given a genetic consultation to clarify possible pathologies.

The specialist examines the medical history and calculates the probability percentage by correlating:

• ultrasound indicators;
• the result of a biochemical blood test;
• mother's age.

If TVP is increased, an additional blood test and repeat ultrasound examination may be prescribed. With secondary confirmation and a risk ratio of 1:300, further studies are recommended:

• Amniocentosis. Collection of amniotic fluid;
• Chorionic biopsy. Taking the cells that form the placenta for analysis;
• Placentobiopsy. Collection of placental cells;
• Cordocentesis. Taking umbilical cord blood or material from embryonic villi for analysis.

The result of each procedure, unlike the previous ones, gives one hundred percent clarity about the presence of TVP pathologies in the fetus.

After receiving the data, the pregnancy is prolonged or recommendations are given for termination for medical reasons. The choice remains with the future parents.

Features of the thickness of the collar space at 12 weeks

At the twelfth week, the embryo has already passed three months of development and the main markers by which conclusions can be drawn about its development are visible to the specialist. This is the most informative stage for identifying various pathologies and abnormalities in the development of the fetus, as well as during pregnancy in general. Each parameter has its own data, which is correlated with the norm table. As for the collar zone, its thickness also has certain limits. The accumulation of fluid that gives rise to a fold in the twelfth week should not exceed 3 millimeters, the minimum size is 0.7 mm. It is important to keep in mind that the data may vary depending on the location of the fetal head: whether it is pressed to the chest, turned to the side, etc.

Features of TVP at 13 and 14 weeks

In the second trimester, at 13-14 weeks of pregnancy, the cervical fold decreases in size. The indicator is gradually becoming irrelevant. At week 13, in the form with the baby’s data, in the line with data on TVP, an indicator from 1.7 to 4 mm can be entered. These figures are within the accepted framework and the risk of developing pathology in the embryo or pregnancy complications in the mother is reduced to a minimal percentage.

Expansion of the collar zone does not always indicate the development of problems in the fetus. It is important to know that its dimensions always correlate with those of other echographic markers obtained during ultrasound examination. If, however, the size of the TVP goes beyond the normal limits, you should not despair. There can be many reasons. In each specific case, they are determined by a specialist with specific qualifications. And depending on the detected anomalies, further actions may be prescribed. It is worth remembering that the result of measuring the collar area is relevant only during the first trimester. Try not to miss this time.

The main task of ultrasound performed on pregnant women is to detect pathologies of fetal development, defects and disorders of gestation, if any. It is important to conduct an ultrasound examination for every woman, regardless of her health and sensations. Expectant mothers may often not be aware of the presence of chronic foci of inflammation in their body or may not attach importance to any teratogenic factor (passive smoking, unfavorable environmental conditions, and so on). All these factors are the reason for mandatory screening studies.

As diagnostic criteria, WHO has identified the most informative ultrasound signs for each trimester of pregnancy. At 10-14 weeks (the time of the first screening), a criterion that identifies the likelihood of developing fetal pathology is the thickness of the nuchal translucency space (TN).

Definition and research methodology

The term TVP refers to the distance between the fetal skin (its internal surface) and the outer surface of the soft tissues covering the fetal neck area. Since the error in measuring this indicator should be excluded, two basic principles for conducting TVP research were identified:

• The duration of the study was from the 11th to the 14th week. Assessing nuchal translucency thickness at other gestational ages will give false results. In this case, the coccygeal-parietal size of the embryo should lie in the range of 45-84 mm;
• ultrasound scanning plane – TVP measurement should be carried out only in the sagittal plane, which ensures maximum accuracy of the study.

As a rule, after the 10th week, the transabdominal examination method is quite sufficient for good visualization of the fetal neck area. The transvaginal ultrasound method is used only in 4% of cases when the ultrasound picture remains unclear with the classical method.

Professor M.V. Medvedev highlighted additional nuances that may affect the results of determining the TVP:

• fetal position - the child's head thrown back gives a false increase in the thickness of the collar space by 0.62 mm. Flexion of the head reduces TVP by 0.40 mm. These are average values ​​that were determined by foreign diagnosticians. A normal individual fluctuation is considered to be a change of +- 0.08 mm. This is important to consider when interpreting the results;
• selection of the image size of the ultrasound device - the optimal scale is 2/3 of the entire ultrasound picture. At this value, the research error will be minimal;
• additional examination of amniotic structures (amniotic membrane, umbilical cord) - in certain positions of the fetus, the differences between these structures and the soft tissues above the cervical spine of the fetus may be erased. According to Professor Medvedev, this is the main reason for false research results. Additional visualization of provisional organs and transvaginal examination help eliminate errors.

All these diagnostic elements must be taken into account so that the study results are reliable and indicate the real presence/absence of fetal pathology.

Normal TVP indicators

The thickness of the collar space is estimated in mm. Based on the results of numerous studies by Soviet and Russian scientists, the average TVP indicators were determined in accordance with the gestational age:

You should pay close attention to the increase in TVP, which is directly dependent on the incidence of developmental pathology. Research data from P. Pandya demonstrates the following results:

Such statistical data allow you to decide on the tactics for further pregnancy management and choose the most optimal option.

Tactics for managing a fetus with increased TVP

Reliable confirmation of an increase in the thickness of the collar space of more than 5 mm is an important diagnostic criterion for a possible hereditary pathology. In this case, a neonatologist or obstetrician-gynecologist may recommend terminating the pregnancy. This decision is completely justified and rational, but the choice remains with the expectant mother.

If she disagrees with the abortion procedure, a full intrauterine diagnosis of the fetus is performed. As a rule, this is only possible in large regional centers for “Maternal and Infant Care” or obstetric hospitals. It is recommended to carry out invasive procedures (amniocentesis, cordocentesis) to determine the chromosome set of the embryo and more accurately assess its condition. Repeated ultrasound examinations are prescribed to visualize the malformation, which is indicated by an increase in TVP.

Forecast

Treating such a child is a very difficult task, even for modern medicine. Since the pathology most often consists of an abnormality of the genetic apparatus, a complete cure is impossible. Such children have a very high risk of disability. Life expectancy, as well as its quality, are significantly reduced, even with constant maintenance therapy. The prognosis for the formation of gross malformations is almost always unfavorable.

Other reasons for the increase in TVP

In case of multiple pregnancy, the development of feto-fetal transfusion syndrome (FFTS) is possible. This situation is quite rare - the incidence is about 4% of multiple pregnancies, according to Professor O.V. Makarova. This pathology is a violation of the blood circulation of the mother and fetus due to the large number of anastomoses between the vessels. The first ultrasound sign of this syndrome is an increase in TVP of more than 3 mm. However, it should be noted once again that this phenomenon is quite rare and does not exceed 2 cases per 1000 pregnancies.

TVP is an important diagnostic criterion for intrauterine pathology in the first trimester of pregnancy. Its direct connection with the risk of developing defects has been proven, so close attention should be paid to the thickness of the nuchal translucency during the first ultrasound screening. This will help you timely choose the right tactics for managing a pregnant woman and adequately assess the chances of bearing a healthy child.

In the first trimester, during which the nuchal translucency norm at 12 weeks plays an important role.

Determination of TVP in combination with biochemical markers is today considered one of the main criteria for the formation of a risk group with chromosomal pathologies. It is believed that a certain period is considered the most informative period, and after 13 weeks of pregnancy such a study does not provide any information.

The nuchal translucency is an accumulation of fluid in the neck area of ​​the fetus.

The nuchal space is the accumulation of a certain amount of fluid in the neck area of ​​the developing fetus. In fact, the presence of a small volume of such fluid is normal for a developing person, but with Down syndrome an excess of the norm is observed.

You should know that measuring just one nuchal space is not enough to confidently state that a child has a chromosomal disease. To evaluate the image of the nuchal translucency, both transabdominal and transvaginal scanning are used in medical practice. The risk of diagnosing chromosomal abnormalities in a child is higher if a large width of the nuchal space is diagnosed.

The size of the collar space itself is not a verdict, but only indicates the presence of a certain risk.

It is possible to draw conclusions about the increased risk of developing chromosomal diseases in a child only if the results are poor and the size of the cervical fold is above 3 mm. In such a situation, to clarify the diagnosis, a chorionic villus biopsy is performed, which makes it possible to refute or confirm the presence of a chromosomal disease in the fetus.

Features of TVP measurement

Experts say that the optimal period for measuring TVP is considered to be 12 weeks. Compliance with precisely these deadlines is due to the fact that performing an ultrasound earlier or later than the proposed deadlines may not carry diagnostic value due to the receipt of incorrect data.

Measuring TVP up to 12 weeks has some difficulties and this is explained by the small size of the fetus. Performing after 12 weeks is undesirable, since after this time the fluid accumulated in the collar area can be actively absorbed by the child’s lymphatic system, which has begun to develop at an accelerated rate.

It is important to remember that before starting to measure TVP, it is necessary to determine the exact stage of pregnancy.

For this purpose, the specialist determines the coccyx - the parietal size of the developing fetus.

To carry out a TVP measurement according to all the rules, the following conditions must be met:

• Ultrasound examination should be performed at 12 weeks
• it is important to maintain the sagittal plane along which the scanning process will be performed
• KTR size should be 45-84 mm

It should be remembered that significant fusion may be influenced by the position of the fetus during the procedure. The TVP indicator can be increased by 0.6 mm if the child straightens his head. When a child presses his chin to his chest, a decrease of up to 0.4 mm may be observed. It is for this reason that we can talk about the reliability of the measurements obtained only if the measurement was carried out with the child in the correct position.

Standard indicators of TVP

During pregnancy, when performing an ultrasound at 12 weeks, the TVP norm should be 0.7-2.5 mm. If there is a thickening of the collar space, then the likelihood of having a baby with chromosomal pathologies increases. It is for this reason that when TVP is 3 mm or more, a specialist prescribes invasive karyotyping.

Thanks to this type of research, it is possible to diagnose at the cellular level the likelihood of having a child with a genetic syndrome. In addition, a chorionic villus biopsy is performed, when a piece of placental tissue is taken for examination.

It is also possible to confirm the risk of parents having a child with chromosomal abnormalities using early amniocentesis, when a sample of amniotic fluid is taken.

It is important to remember that the risk of diagnosing various abnormalities in a baby increases with the age of the expectant mother. When the collar space thickens, the specialist pays attention to the size of the nasal bone, because with pathologies of a chromosomal nature, there is a discrepancy between its size and the term. In addition, with such deviations, a shortened upper jaw can be diagnosed, which makes the contours of the face smoother.

Chromosomal pathologies and abnormalities in TVP

The risk of developing chromosomal abnormalities in an unborn child is directly proportional to the increase in TVP.

Medical practice shows that the following pathologies are most often diagnosed:

• Down syndrome
• Patau syndrome
• Turner syndrome
• Edwards syndrome

The diagnosis of such disorders is associated with trisomy, when an extra chromosome is detected. In addition, monosomy, which is characterized by the absence of one chromosome, is possible. If complex defects incompatible with life are detected in the expectant mother, she is offered an artificial termination of pregnancy. When determining Down syndrome, parents have the right to independently decide whether to terminate the pregnancy or continue it.

An increase in the size of the nuchal translucency has a direct relationship with genetic chromosomal defects and congenital malformations.

At the same time, one should not completely equate an increase in TVP with a mandatory termination of pregnancy, because parents often give birth to completely healthy children without any defects or abnormalities. Expansion of the nuchal translucency is considered only one of the indications for a more detailed examination of the expectant mother, which will make it possible to diagnose congenital malformations.

Useful video - 12th week of pregnancy: development of mother and baby.