Can the thickness of the collar space decrease? What is TVP? When are TVP measurements taken?

From 12 to 40 weeks, the fetal period of development of the unborn baby begins. At this time, all organ systems are not yet functionally developed. Week 13 is the period of manifestation of local motor reactions of the fetus. The nervous, respiratory, endocrine, and skeletal systems of the fetus continue to actively form. The features of your future baby become more expressive. The 13th week of pregnancy is the initial period of manifestation of the first emotional reactions of the unborn baby.

Fetal development at 12-13 weeks

To assess the development and diagnosis of fetal pathology, fetal fetometry is performed at 12 or 13 weeks.

Fetometry parameters and their norm for the fetus at the 13th week of pregnancy:

• biparietal – 24 mm;
• thigh length – 12 mm;
• chest circumference – 24 mm.

At 13 weeks, the embryo weighs 31 g and is 10 cm tall.

TVP at 13 weeks

The thickness of the nuchal translucency or TVP is a parameter that doctors pay attention to during ultrasound screening at the 13th week of pregnancy. Nuchal translucency thickness is an accumulation of fluid on the back of the fetal neck. Determining this parameter is important for diagnosing genetic abnormalities of fetal development, in particular in determining Down, Edwards, and Patau syndrome.

TVP at 13 weeks is normal

The normal physiological value of the thickness of the nuchal translucency is 2.8 mm at 13 weeks. A small amount of liquid is typical for all babies. An increase in the thickness of the collar space of more than 3 mm indicates the possible presence of Down syndrome in the unborn baby. To confirm the diagnosis, it is necessary to conduct additional invasive examinations, which can be dangerous for the baby. The risk of developing this pathology is especially increased during the first pregnancy after 35 years.

Remember that the diagnosis of increased thickness of the collar space does not indicate one hundred percent presence, but only allows you to determine the risk group among pregnant women.

Currently, there are many methods of examining a pregnant woman to determine the condition of the fetus, but the most informative and priority is ultrasound. During the period of bearing a child, women undergo ultrasound diagnostics several times.

In this case, special attention is paid to the thickness of the collar space. The value makes it possible to detect chromosomal abnormalities in the fetus, starting from the first trimester of pregnancy.

TVP: what is it?

The collar space is an accumulation of fluid in the baby's cervical area. Its volume is of primary importance, since expansion of the nuchal space may indicate chromosomal changes.

Increased thickness of the collar space indicates a potential risk. True, an echographic marker alone is not enough to accurately determine a genetic abnormality.

For the first time, the slit-like area of ​​the baby’s neck is examined at 11-14 weeks of pregnancy. With normal development of the baby, after the 15th week of pregnancy, the collar space will decrease and later disappear altogether. In exceptional situations, the lymph cannot cope with the absorption of fluid, which causes edema or hygroma to form.

Determining the size of the nuchal cavity in the fetus at 12 or 13 weeks of pregnancy is a mandatory first screening procedure. In addition, there are categories of families for which measuring TVP is of particular importance:

• the potential mother is over 34 years old, and the father is 41;
• the couple already has a child with a chromosomal aberration;
• the woman has a history of abortion or stillbirth;
• one of the parents has a chromosomal aberration or mosaicism;
• the potential mother or father was in the radiation zone or in contact with another mutagenic factor.

How is the thickness of the collar space determined?

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Often, the measurement of TVP in the fetus is carried out using the usual transabdominal ultrasound diagnostic method. In the early stages of pregnancy (at 11, 12, 13, 14 weeks), the transvaginal method is sometimes used. Basically, an examination using a vaginal sensor is prescribed if the baby is difficult to see with a regular ultrasound.

During transvaginal diagnosis, a woman must undress to the waist. There should be no pain during the procedure, but a small amount of blood on the device is considered normal.

Before measuring the thickness of the fold in the collar area, the specialist will calculate the growth of the fetus, or rather the distance from the crown of the baby to its tailbone. When determining TVP, it is important that the baby's head is in a neutral position. If the position is inappropriate, the indicator will be increased or decreased. To get a reliable result, you must wait until the baby takes the correct position (for this, the pregnant woman is recommended to cough).

Using scaling, the echographer will enlarge the area of ​​the fetal neck, after which he will take measurements of the nuchal fold and the fluid accumulated under it. On the screen, the liquid has a black tint, and the baby’s skin and tissues are white. In the picture, the collar space is indicated in blue. After calculation, the specialist compares the values ​​with established standards.

Norms for the thickness of the collar space

The optimal period for conducting the study is 12 full obstetric weeks, but it is permissible to conduct screening 7 days earlier or later than the specified period. In this case, the CTE of the fetus should reach 45 mm and not exceed 84 mm.

The normal TVP is 0.7-2.8 mm depending on the week of pregnancy. More information about the norms of TVP in accordance with the gestational age of the fetus can be found in the table.

If, as a result of diagnostics, it is determined that the thickness of the collar space is below normal, there is no cause for concern. The risk of chromosomal aberration exists only with elevated values.

If the thickness of the collar space exceeds or equals 3.4 mm, then we may be talking about Down syndrome. TVP expansion greater than 5.5 mm may indicate chromosomal Edwards disease.

When the collar space thickens, the length of the upper jaw and nasal bone must be determined. Inconsistency in size also indicates pathology. In addition, the intracranial space is important; the norm in the fetus at the 12th week of pregnancy is 1.5-2.5 mm.

What do deviations from the norm mean?

In most cases, when the diagnosis revealed a too wide cervical fold, the babies were born healthy. The probable presence of a chromosomal abnormality is indicated when, in addition to the expansion of the nuchal translucency, other examination results are obtained that confirm the pathology.

The reliability of TVP measurements depends not only on the specialist’s experience and the condition of the equipment, but also on the position of the baby’s head during diagnosis. So, if the baby is placed incorrectly, the consequences will be errors - the indicator will decrease by approximately 0.4 mm if the child presses his head to the chest, and will increase by 0.6 mm if the baby throws it back too much. In this case, the value should be measured strictly along the inner contour of the neck fold. The correct gestational age is also of great importance.

It is worth noting a number of reasons influencing the increase in fluid volume in the collar area:

• cardiac system disorders;
• infection;
• anemia;
• poor blood circulation;
• pathologies of the vascular system;
• decreased protein content in blood serum;
• disorders of the skeletal system.

These pathological problems are characteristic of various chromosomal aberrations. Thus, expansion of the fold in the neck area occurs in more than fifty pathologies of genetic origin, as well as in the death of the embryo in the womb. The most common chromosomal aberrations are:

• Down syndrome;
• trisomy 13;
• Shershevsky-Turner syndrome;
• Edwards syndrome.

What to do if an anomaly is detected?

It is possible to find out whether a child has a chromosomal disorder only through an extensive examination. If the TVP value is greater than normal, pregnant women are recommended to undergo ultrasound diagnostics again after a week. A study of biochemical markers in the blood - free beta-hCG and PAPP-A - is also carried out. In this case, the age of the potential mother must be taken into account.

Based on the results of the screening, a conclusion is issued indicating the risk of having a baby with a chromosomal abnormality. If there is a high probability of a chromosomal aberration, the pregnant woman will be referred for a number of other studies. Moreover, any of them is carried out only at the request of the woman; she has the right to refuse. As an additional examination, the following may be prescribed:

• Chorionic villus biopsy - checking a small particle of chorion;
• placental biopsy - study of placental cells;
• amniocentesis - a study of amniotic fluid, is prescribed if the obtained biopsy result is inaccurate or the chorion sample is destroyed when studied in the laboratory;
• cordocentesis - diagnosis of blood from the umbilical cord or material from the villi of the embryo.

The goal of each study is to determine the set of chromosomes. If it consists of 23 chromosomes, it means everything is normal. If there are critical indicators, termination of pregnancy is recommended.

And now I want to write about another recent incident that occurred in my residential complex...
Me 04.05.12 According to my doctor’s calculations, I should have been issued maternity leave. Plus I was scheduled for an ultrasound with Doppler. I had an ultrasound, took the results and went to see a doctor. When I had this ultrasound with Doppler, the ultrasound specialist said that everything was fine with the baby, but her weight was somehow too small for 30 weeks, only 1250 kg. I explain to her that my baby is now NOT 30 weeks in utero development, but approximately 27, since the conception was much later, therefore the difference is 3 weeks and its size is not for a 30-week-old baby, but for a 27-week-old. And I am 30 weeks according to the date of the first day of my last menstruation. The ultrasound specialist said that since the doctor puts you at 30 weeks, that means the baby is 30 weeks (apparently she didn’t even listen to me what I meant). As a result, she gave me her Conclusion that everything was OK, but the baby was 30 weeks old, and her weight was insufficient, she diagnosed fetal hypotrophy + suspicion of insufficient nutrition from the placenta to the umbilical cord.
I'm panicking again...
I took this conclusion and went to see my doctor that same day. My doctor who sees me constantly (I am a paid member of her) calculated my maternity leave date as 05/04/2012, because... this is 30 weeks from the first day of the last menstruation (09.10.2011). When I came to the appointment, my doctor turned out to be on sick leave and would only be released on May 10, 2012.
Her replacement doctor saw that my maternity leave date was 05/04/12. She said that she wouldn’t give me maternity leave today, citing the fact that the date of maternity leave should be calculated based on the first ultrasound visit, i.e. They look at the size of the fetus and accurately determine the duration of my pregnancy! And the period according to ultrasound differs from the period of menstruation by three weeks. That is, now (as of 05/04/12) according to ultrasound I am 26-27 weeks, and according to the date of my last menstruation I am 30 weeks. In general, she told me to wait for my doctor to come out and take a maternity leave from her; she herself would not give it to me, because they give her a hard time if she gives maternity leave ahead of schedule.
All this substitute doctor gave me was a sick leave certificate and that’s it!
Moreover, having seen the latest ultrasound results from their LC consultation where they allegedly discovered that I was not underdeveloped by the fetus at 30 weeks, she yelled and told me to go to the hospital!!
Now go to these doctors!!! After all, to get to a good ultrasound specialist, you need to pay money in most cases, but many expectant mothers simply don’t have it! Why should people suffer because of such medicine?
If I had listened to the doctors now, I would have gone to the hospital and now they would have given me medications that I don’t need at all!

In short, because of such negligent treatment of doctors (one period was not recalculated so that the period coincided with the date of the ultrasound and not with the menstrual period, the ultrasound specialists relied on this and considered that it was so, that the baby was really 30 weeks in utero) to go to again Voevodin in Moscow, who again CONFIRMED NOTHING, said that your baby in utero is really 27 weeks old, that my Doppler is good, I don’t need to go to the hospital, otherwise I could harm her. With his Conclusion, I went to the doctor on May 21, 2012 (already to my doctor, who returned from sick leave and recalculated my maternity leave as normal), took Voevodin’s Conclusion. Now I will have a normal Doppler in this LCD at the 32nd intrauterine week, the date of visit is scheduled for 06/05/12. Now the date of 32 weeks coincides with the date of the baby’s intrauterine weeks.

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 translucency 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.

The collar space is a fluid-filled area located from the skin to the soft tissues on the neck of the unborn child. This structure is detected in every fetus, however, with various developmental anomalies, a change in its size is observed; it is a criterion for normal intrauterine development.

TVP (stands for nuchal translucency thickness) is a parameter examined by ultrasound. It can be used to suspect chromosomal abnormalities and other pathologies in the fetus. If TVP exceeds the norm, a more thorough diagnosis is recommended to confirm or refute the diagnosis.

Measuring the thickness of the collar area

At the first screening, in addition to ultrasound diagnostics, a biochemical blood test is performed for placental hormones, which may also indicate the possibility of chromosomal abnormalities in the fetus. However, if this test is normal and the TVP is expanded, the woman should be examined by a geneticist to clarify the diagnosis.

Attention! The expansion of TVP in the fetus during the first screening does not indicate a 100% probability of the presence of congenital anomalies, so expectant mothers should not immediately panic; they need to have a repeat ultrasound from another doctor or additional studies.

When measuring TVP, the following rules must be observed:

• the ultrasound sensor must be in the sagittal plane;
• the unborn child should not be pressed against the uterus;
• the image should only show the head and half of the chest;
• the head should be in a free position, not bent or straightened;
• TVP is determined by the widest dimension of the neck fold.

Standard collar thickness

The thickness of the collar space during the 13th week is on average 1.7 mm, normally it can increase to 2.7 mm. After 14 weeks, TVP is not measured, since the fluid in the cervical fold tends to resolve during this period.

Table of norms for the thickness of the collar zone:

Possible deviations from the norm

The expansion of the TVP is formed as a result of pathologies caused by chromosomal abnormalities:

1. Violation of fetal cardiac activity.
2. Disruption of lymph outflow.
3. Stagnation of blood in the upper parts of the body.
4. Skeletal anomalies.

Consequences of thickening of the collar area

If, using additional research methods, a severe fetal anomaly is detected, and the gestational age is less than 22 weeks, experts recommend that the woman have an abortion for medical reasons. This procedure is safe in a hospital setting. After some time, you can try to have a child again.

If the pregnancy is 22 weeks or more, the woman is offered to terminate it using artificial labor, or preserve the fetus. The expectant mother should be well informed by specialists about the consequences and make her informed choice. When using invasive diagnostic methods, false positive results account for no more than 0.5% of all studies. Therefore, if a woman is not ready to raise a child with pathologies, she should give preference to terminating the pregnancy.