The thickness of the collar zone is 12 weeks. Why is the thickness of the collar space of the embryo examined? How the results are evaluated
In the first trimester of pregnancy, all women undergo a planned ultrasound, in which the doctor determines various indicators that reflect the condition and development of the fetus. Among them, attention is paid to the indicator of the thickness of the collar space (TVP). Its measurements determine the risk of having a baby with Down syndrome, Edwards, Patau and other chromosomal abnormalities.
What does collar space mean?
Collar space- subcutaneous accumulation of fluid in the neck at the back of the head, displayed on ultrasound as a black stripe. The assessment of the thickness of the collar space of the fetus is informative only for a period between 11 and 13 weeks, with a coccygeal-parietal size of 45-84 mm. After 13 weeks, the accumulation of this subcutaneous fluid resolves.
TVP norm indicator
The thickness of the collar space is up to 3 mm. However, an increase in this indicator does not indicate the presence of a chromosomal abnormality in the fetus, it only enrolls a woman in a risk group. The accuracy of the diagnosis can be confirmed only after passing additional studies.
TVP norm by week
What to do with increased TVP
With an increase in TVP, the presence of other signs of chromosomal abnormalities will also be taken into account, such as the size of the nasal bone, impaired blood flow in the venous duct, hyperechoic focus (brightness of a small area of the heart muscle on ultrasound) in the heart. Based on these data, a pregnant woman may be recommended to undergo a chorionic villus biopsy or amniocentesis to clarify the diagnosis. All these diagnostics can cause a miscarriage, so they are carried out only in case of a high risk of genetic pathology.
Chorionic villus biopsy
The analysis can be taken through the cervix or abdomen between 11-13 weeks. During an abdominal biopsy, the skin of the abdomen is treated with iodine solution, then the place is anesthetized and a long thin needle is inserted into the abdominal cavity, through which a piece of placental tissue is taken. When conducting a transcervical biopsy, the vagina is treated with an antiseptic, then the probe is inserted into the placenta and tissue is taken for examination.
Both biopsy methods are performed under ultrasound, which allows you to determine the exact direction of the needle or probe. On average, the duration of the procedure is about 15-20 minutes. After the procedure, the resulting tissue sample is sent to the laboratory for analysis.
Amniocentesis
Amniocentesis is performed between 15 and 18 weeks of pregnancy. A small area of the skin of the abdomen is treated with an antiseptic and local anesthesia is applied. Using ultrasound, the location of the fetus and placenta is determined, then a long, thin needle is inserted into the abdominal cavity and a small amount of amniotic fluid is collected, which is sent to the laboratory for analysis.
After the procedure, a pregnant woman may experience colic and slight discomfort in the abdomen. The rest of the day the pregnant woman should spend lying down, you can not lift weights and you should refrain from sexual intercourse.
Causes of increased TVP in the fetus
The accumulation of fluid in the crease of the neck can be caused by several reasons. Some are associated with the presence of chromosomal abnormalities in the fetus:
- Down syndrome - an extra chromosome is present (47 instead of 46). It is characterized by an abnormal structure of the face, body, underdevelopment of the psyche and internal organs in the fetus.
- Patau syndrome - an extra chromosome is also observed (47). It is manifested by underdevelopment of the brain, internal organs, an abnormal structure of the face, the presence of extra fingers and toes.
- Turner's syndrome - the presence of only one X chromosome in the fetus. It occurs only in girls. It is characterized by short stature, deformation of the auricles, elbows, shield-like chest, skin pigmentation, and mental retardation.
There are reasons not related to chromosomal abnormalities:
- anemia;
- heart defects;
- violations in the development of the skeleton;
- violations in the formation of connective tissue;
- reduced amount of protein in the blood plasma;
- deviations in the work of the lymphatic system.
Factors that may affect the study
The results of a TVP study can be influenced by several factors that can distort the data:
- professionalism of the ultrasound diagnostician;
- state of the ultrasound machine;
- taking measurements along the inner contour of the neck fold, and not along the outer;
- the position of the fetal head during ultrasound.
It is worth paying attention to the position of the fetal head during the study, which can affect the thickness of the collar zone. Extension of the head by the fetus can increase this figure by 0.6 mm, and pressing it to the chest will decrease the figure by 0.4 mm. Therefore, the measurement of the TVP parameter is not able to give unambiguous answers to the question of whether pathology is present or not.
If in the course of additional studies (amniocentesis or chorionic villus biopsy) the presence of chromosomal abnormalities in the fetus is detected, then the woman is recommended artificial termination of pregnancy.
Views: 4891 .During the stay of the baby in the womb, a woman undergoes numerous studies and tests. Such diagnostics are necessary in order to know the health status of the expectant mother and her baby. A mandatory examination during pregnancy is an ultrasound scan. It is this diagnosis that makes it possible to identify possible deviations and disturbances in the development of the embryo. In this article, we will talk about what is the norm of the thickness of the collar space at 13 weeks. You will learn how the examination of this education is carried out. Also get acquainted with the possible problems that arise if the collar space of the baby does not fit into the allowable values. It is worth saying a few words about what needs to be done in case of deviation from the norm.
What is the collar section of the fetus
To begin with, it is worth saying what a collar space is. This is a place where fluid accumulates between the baby's neck and upper skin. This formation most often has an oblong shape.
On the monitor of the ultrasound machine, it is displayed in black. Whereas the skin has a white tint. Width measurement is carried out at the widest point of this formation.
The norm of the thickness of the collar space at 13 weeks: how the examination is carried out
At this time, the expectant mother is examined using a transabdominal sensor. In some cases, when it is difficult to establish the right one, the transvaginal method can also be used.
The woman lies on a flat couch on her back. The specialist must use a conductive gel before starting the diagnosis. It facilitates transducer movements and improves sound conduction.
The position of the fetus during diagnosis should be lateral. Only in this state can a specialist see an accurate cut and measure the cervical region.
How does the collar space (norm) depend on the gestational age
The measurement of this object should be made in the period from 11 to 14 weeks of baby development. This limitation is due to the following. At 10 weeks, the size of the fetus is still very small, and some experts fail to catch the desired position of the crumbs. After that, a gradual decrease (resorption) of this accumulation of fluid begins. In this regard, the diagnosis at this time may be uninformative.
The collar space (norm) increases in size from 10 to After this period, it begins to gradually decrease, practically disappearing by the 16th week of embryo development.
The norm of the width of the cervical region of the fetus
There is an established for all (norm). A table of valid values is provided in this article.
If the expectant mother undergoes ultrasound diagnostics at 11 weeks of baby development, then for this fetus, the allowable values for the width of the formation are in the range from 0.8 to 2.2 millimeters.
In the case when the diagnosis is carried out at a period of 12 weeks of pregnancy, the norm of the collar zone has boundaries similar to the previous period. So, the range of values is from 0.8 to 2.2 millimeters. But it is worth noting that the same fetus cannot have the same data in different weeks of pregnancy.
The norm for the thickness of the collar space at 13 weeks is as follows: from 0.7 to 2.5 millimeters. A few days later, the distance can already reach 2.7 millimeters, which is also a normal indicator.
In addition to the allowable width, the specialist also notes the minimum boundaries. The norm of the thickness of the collar space at 13 weeks or earlier should not be less than 0.3 millimeters. Otherwise, we can talk about the thinning of this zone.
Also, when measuring, it is worth considering the position of the fetus. The head of the embryo should lie horizontally and be at the same level as the body. If the future baby bends the neck and presses the chin to the chest, then the width of the collar zone may be underestimated. It also happens in the opposite case. If the baby tilts the head back, then this segment expands. These conditions must be taken into account when taking measurements.
Deviations from normal values
If it is diagnosed that the collar space does not fit into the range of acceptable values at 13 weeks (the norm has not been identified), what should be the further actions in this case? Most often, this result indicates a possible chromosomal abnormality. So, thinning or expansion of the collar space in the fetus indicates the presence of Down syndrome.
In this case, the specialist issues an ultrasound protocol with a conclusion that indicates the possibility of pathology. Most often, the doctor prescribes an additional examination, which is carried out in one or two weeks (if time permits). Also, the expectant mother is recommended to take a blood test to determine the risks. It is this diagnosis, in conjunction with an ultrasound examination, that makes it possible to establish the presence of chromosomal pathology as accurately as possible.
What to do if an anomaly is found
If an additional examination showed the presence of Down syndrome or another, then the woman is offered to conduct a series of additional studies. Most often, the diagnosis consists in taking material from the umbilical cord or fetal bladder. After the examination, a reliable conclusion is made. If congenital malformations are confirmed, a woman may decide to terminate the pregnancy.
Does everyone have the same rate at 13 weeks of pregnancy
It is worth noting that you can not rely on the data of your friends or relatives. If in one fetus the thickness of the collar zone was, for example, 1.3 mm, and in another 2.0 mm, then this is a normal value. Do not sound the alarm and say that the second child has risks. The data fits within the allowed values and this is the most important thing.
Often normal values can be somewhat smeared. On different devices and on different days, the width of this formation may differ by several millimeters. This is not critical.
Every pregnancy is different. What happened the first time can be radically different from everything that happens in the second.
Summing up and conclusion
Be sure to go through all the tests prescribed by your doctor. Only in this case you will be sure of the health and normal development of your unborn child. Never give up the first one. After all, it is this diagnostic that allows you to identify possible deviations in
The width of the cervical region is an important indicator. Now you know what is the norm of the thickness of the collar space at 13 weeks of pregnancy and at an earlier (later) time. Try to undergo ultrasound diagnostics from the same specialist. In this case, the data will be as reliable as possible. Have an easy pregnancy and good results in the thickness of the collar space of the fetus!
The image of the collar space can be assessed using both transabdominal and transvaginal scanning. Assessment of TVP in the fetus is carried out at values of the coccyx-parietal size (KTR of the fetus) from 45 to 84 mm and allows suspecting chromosomal abnormalities, especially trisomy of the 21st chromosome (Down syndrome) and forming a risk group for the birth of children with congenital and hereditary pathologies among pregnant women .
The thickness of the collar space. Norm
The thickness of the collar space is normally from 0.7 to 2.7 mm depending on the gestational age. The risk of having a child with chromosomal abnormalities increases markedly with the thickening of the collar space and the age of the mother. Therefore, whenever the thickness of the collar space is 3 mm or more, the doctor prescribes an invasive karyotyping (a study that allows you to identify at the cellular level the possibility of having a baby with a genetic syndrome, such as Down syndrome, Edwards, Patau, etc.), using a chorionic villus biopsy (a piece of placental tissue is taken for analysis) or early amniocentesis (in order to obtain a sample of amniotic fluid).
For young women (under 35 years old) who do not have increased risk factors for chromosomal abnormalities, non-invasive screening ultrasound and blood donation for biochemical markers (PPAP-A, hCG, AFP) may be recommended.
Simultaneous consideration of the mother's age, embryonic TVP and the results of determination of free β-hCG and PAPP-A in the mother's blood serum makes it possible to more accurately confirm or refute the possibility of giving birth to a child with chromosomal abnormalities, as well as reduce the number of invasive interventions.
Despite the presence of a direct relationship between the frequency of chromosomal defects, congenital malformations and the expansion of the nuchal space in the fetus in the early stages of pregnancy, TVP cannot be fully identified with the need for abortion, since healthy children are born in more than 80% of cases. The expanded collar space is only an indication for a more detailed and extended examination, in particular for the timely diagnosis of congenital malformations that may appear later than the detection and disappearance of TVS.
Particular attention during the ultrasound examination in the first three months of pregnancy is paid to the parameters of the first spine in the fetus.
The thickness of the collar space at the 12th week of pregnancy determines the presence of genetic indicators in relation to chromosomal abnormalities, which is a fundamental point in the period.
During the period of intrauterine gestation, a number of ultrasound examinations are prescribed, the main purpose of which is to determine gross pathological processes in the development of the fetus and the general state of pregnancy.
The first planned is carried out at 12 weeks of pregnancy.
At this time, the thickness of the collar zone is determined, by which it is possible to determine the presence of chromosomal congenital pathologies.
At later stages, the collar zone resolves, which does not allow establishing the presence of violations in the development of the fetus.
The nuchal zone is an area that is located in the interdimensional region of the inner side of the first section of the embryonic spine and the tissue that covers the neck and spine. This area is an accumulation of fluid in the subcutaneous tissue, which is subsequently absorbed.
Measurements of the parameters of the collar space in thickness are carried out at the time of the first ultrasound screening study at 11-12 weeks of pregnancy, since the accumulation of subcutaneous fluid decreases at a later date.
On average, the normal indicator for measuring the collar zone is a size of no more than 3 mm. At week 11, the size of the neck fold can reach
maximum dimensions, but not more than 1-2 mm. By week 12, its dimensions are 1.8-2.9 mm. Week 13 allows a size of 3 mm, all other indicators exceeding the allowable parameters are a signal of the need for an additional thorough examination.
With a transvaginal ultrasound examination at a gestational age of twelve weeks, the collar zone in terms of thickness should not exceed 2 millimeters.
It is worth considering the fact that the thickness of the neck fold is also affected by the position of the fetus. If the head is unbent, the indicators increase by an average of 0.6 mm, and when the chin touches the chest, they decrease to 0.5 mm.
In order to most correctly examine the thickness of the collar zone in the fetus, it is recommended to use the services of a highly qualified specialist who uses modern ultrasound equipment.
Exceeding the norm and additional examination
An ultrasound examination of a pregnant woman in order to measure the thickness of the collar space is mandatory in the following cases:
- Sagittal scan of the fetal head
- 10 to 13 weeks pregnant
If, according to the results of ultrasound diagnostics, excesses of the norm of permissible parameters are established, a more thorough comprehensive examination is prescribed for the woman.
It includes:
- Clinical examination
- Re-examination of the thickness of the collar space with the measurement of additional indicators
- by biochemical markers
If, according to the results of a complete additional examination, a high probability of the appearance of fetal chromosomal abnormalities is established, the pregnant woman is included in the risk group. To determine the genetic set of the embryo, invasive prenatal diagnosis is carried out by
transabdominal sampling of material:
- Chorionic biopsy - collection of cells with which the placenta is formed
- Placentobiopsy - collection and examination of cells
- Amniocentesis - by performing a puncture of the amniotic sac, amniotic fluid is taken
- Cordocentesis - sampling of blood fluid from the umbilical cord or sampling of biomaterial from the villi of the embryonic fetus
Based on the results of all combined examinations, a chromosome set is determined. If their number is 23 pairs, the fetus is preserved and the pregnancy continues.
In the case of critical indicators, a decision is made to terminate the pregnancy.
The most common anomalies depending on TVP at 12 weeks of gestation:
- Turner syndrome
- Edwards syndrome
- Patau Syndrome
The decision to terminate a pregnancy or the appointment of drug therapy is carried out exclusively by a doctor. Only he can calculate the probability of having a baby with genetic abnormalities. But the final decision on the prolongation of pregnancy or it remains solely with the woman.
Diagnostic examination of the thickness of the collar space is a significant manipulation in monitoring the development of the embryo. Determination of the coefficient of pathology allows timely detection of abnormal development of the fetus.
You will learn about the diagnosis of Down syndrome from the video:
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The collar space is a fluid-filled area located from the skin to soft tissues on the neck of the unborn child. This structure is detected in each fetus, however, with various developmental anomalies, a change in its size is observed, it is a criterion for normal intrauterine development.
TVP (stands for the thickness of the collar space) is a parameter examined by ultrasound. With the help of it, chromosomal abnormalities and other pathologies can be suspected 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 space
The thickness of the nuchal space should be examined at each pregnancy at the first screening between 10 and 14 weeks. This examination is shown to absolutely all women, since it is one of the most reliable criteria for the normal development of the fetus. The thickness of the collar zone is determined along with the structural features of the nasal bone - another marker for the presence of developmental anomalies.At the first screening, in addition to ultrasound diagnostics, a biochemical blood test for placental hormones is performed, which may also indicate the possibility of chromosomal abnormalities in the fetus. However, if this test is normal and TP is enlarged, the woman should be examined by a geneticist to clarify the diagnosis.
Attention! Expansion of the TVP in the fetus during the first screening does not yet indicate a 100% probability of the presence of congenital anomalies, so expectant mothers should not immediately panic, they need to repeat an ultrasound scan from another doctor or additional studies.
Measurement of TVP during pregnancy should be carried out by a qualified specialist in order to avoid unpleasant stressful situations for the expectant mother. This parameter is measured strictly between the 10th and 14th weeks of pregnancy, since before that it cannot be detected, and after that the fluid in the collar zone resolves and is not visible during ultrasound. The coccyx-parietal size of the fetus should be from 4.5 to 8.4 cm.
When measuring TVP, the following rules must be observed:
- the ultrasound probe must be in the sagittal plane;
- the unborn child should not be pressed against the uterus;
- the image should contain only the head and half of the chest;
- the head should be in a free position, not be bent or unbent;
- TVP is determined by the widest size of the neck crease.
The norm of the thickness of the collar space
Before 10 weeks of gestation, TVP cannot be reliably measured., then the indicator should be in certain values, which practically do not change until the 14th week. With an increase in gestational age, the average value of the parameter increases by only 1-2 mm every 7 days. The thickness of the collar space at the 12th week of pregnancy averages 1.6 mm, but its increase to 2.5 mm inclusive is considered the norm.The thickness of the collar space during the 13th week averages 1.7 mm, normally it can increase up to 2.7 mm. After 14 weeks, TVP is not measured because the fluid in the neck crease tends to be resorbed during this period.
Table of norms for the thickness of the collar zone:
Possible deviations from the norm
An increase in TVP in the fetus may indicate chromosomal abnormalities, and the greater the deviation from the norm, the higher the likelihood of an unpleasant diagnosis. Most often, the expansion of the neck fold is observed in syndromes, Patau (three 13 chromosomes), Edwards (three 18 chromosomes), Turner (one X chromosome).TVP expansion is formed due to pathologies caused by chromosomal abnormalities:
- Violation of the cardiac activity of the fetus.
- Violation of the outflow of lymph.
- Stagnation of blood in the upper parts of the body.
- Skeletal anomalies.
Consequences of thickening of the collar zone
If an increase in the collar zone is detected on ultrasound, the study should be repeated and a biochemical blood test for placental hormones should be performed. If the results of these examinations are outside the normal values, the woman is recommended to conduct additional invasive diagnostic methods. These include amniocentesis (examination of amniotic fluid), cordocentesis (taking blood from the umbilical cord) and choriobiopsy (taking chorionic villi for examination).If, with the help of additional research methods, a severe anomaly of fetal development 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 a while, you can again try to have a baby.
If the gestational age is 22 weeks or more, the woman is offered to terminate it with the help of an artificial birth, or save the fetus. The expectant mother should be qualitatively informed by experts about the consequences and make her informed choice. When using invasive diagnostic methods, false positive results do not exceed 0.5% of all studies. Therefore, if a woman is not ready to raise a child with pathologies, abortion should be preferred.