With the onset of pregnancy, many questions begin to bother a woman. Every expectant mother wishes her baby normal formation and development. In the early stages, there may be risks of developing certain embryo diseases. To study the condition of the baby, doctors prescribe 1 trimester screening. Standards for ultrasound (a photo of the examination is usually attached), a woman can find out from a specialist who is watching her.
What is perinatal screening?
Perinatal screening involves a study of a pregnant woman, which allows to identify various malformations of the child at the stage of fetal development. This method includes two types of examination: biochemical blood test and ultrasound examination.
The optimal period for conducting such an examination is determined - this is a period from ten weeks and six days to thirteen weeks and six days. There is a certain norm for screening ultrasound of the 1st trimester, with which the results of examination of a pregnant woman are compared. The main task of ultrasound at this time is to identify serious malformations of the embryo and identify markers of chromosomal abnormalities.
The main anomalies are:
- TBP size - the thickness of the collar zone space;
- underdevelopment or lack of nasal bones.
Ultrasound during pregnancy allows you to identify signs of a disease such as Down syndrome, and some other pathologies of the development of the fetus. The screening rate (ultrasound) of 1 trimester should be analyzed before 14 weeks. After this period, many indicators are already uninformative.
Screening of the 1st trimester: norms for ultrasound (table)
To make it easier for a doctor to determine the condition of a pregnant woman, there are certain tables of indicators of the development of the baby's organs. The ultrasound protocol itself is structured in order to understand the dynamics of the formation and growth of the embryo. The article presents the screening norms of 1 trimester.
Transcript of ultrasound (table below) will help to obtain information on whether everything is in order with the fetus.
| Name of the organ (criterion) | Norm indicators | Pregnancy terms (weeks) |
| KTR (size from coccyx to crown) | | |
| Heart rate (heart rate) | - 161-179 bpm
- 153-177
- 150-174
- 147-171
- 146-168
| - tenth week
- eleven
- 12
- 13
- fourteen
|
TVP | - from 1.5 to 2.2 mm
- 1.6-2.4
- from 1.6 to 2.5
- up to 2.7 mm
| - tenth
- eleventh
- twelfth
- thirteenth
|
Yolk sac | rounded shape, diameter - organ 4-6 mm. | up to twelve weeks |
Determination of embryo viability
To assess the viability of the embryo, it is very important to see the heartbeat in the early stages. In a small person, the heart begins to beat already in the fifth week of being in the womb of the mother, and it can be detected using screening of the first trimester (ultrasound norms) as early as seven weeks of fetal life. If a heartbeat is not detected at this time, we can talk about the likelihood of fetal death (missed pregnancy).
To assess the viability of the embryo, heart rate is also taken into account, which, normally for a period of six weeks, ranges from 90 to one hundred and ten beats per minute. These important indicators of screening for the first trimester, the norms of ultrasound along with the study of blood flow and body length should correspond to reference data on the gestational age.
The more modern equipment is used for examination, the better you can see all the organs and get the most accurate results. If there is a high probability of having congenital malformations or genetic developmental abnormalities, then the pregnant woman is sent for a deeper examination.
In some regions, when registering in antenatal clinics, screening for the first trimester is mandatory for all pregnant women. The standards for ultrasound may not coincide with the results, therefore, doctors immediately take the necessary measures to preserve the life and health of the child or mother. But most often, pregnant women at risk are referred to such an examination: these are women from thirty-five years old, those who have genetic diseases in the family and previously born children have had miscarriages in previous pregnancies, stillbirths or an undeveloped pregnancy. Close attention is also paid to expectant mothers who have had viral diseases at the beginning of pregnancy, are taking dangerous medications or are exposed to radiation.
If a woman has spotting in the first trimester, then an ultrasound scan makes it possible to identify the degree of viability of the child or his death.
Pregnancy terms
An additional examination to determine the exact gestational age is indicated for women who have an irregular menstrual cycle or who do not even know approximately the date of conception. For this, in most cases, 1 trimester screening is used. Norms on ultrasound, decoding of the main indicators and the date of conception do not require special medical knowledge. The woman herself can see the estimated date of birth, gestational age and the number of embryos. Basically, the number of weeks, determined by ultrasound, corresponds to the period that is calculated from the first day of the female cycle.
Carrying out the study, the doctor makes control measurements of the size of the embryo. With the data obtained, the specialist compares the screening rates of 1 trimester. Ultrasound decryption occurs according to the following parameters:
- measuring the distance between the sacrum and the crown of the embryo (7-13 weeks), which makes it possible to determine the actual gestational age using special tables;
- measuring the length of the parietal bone of the head of the unborn baby (after 13 weeks), this is an important indicator in the second half of pregnancy;
- determining the size of the longest - the femur of the body of the embryo, its indicators reflect the growth of the child in length (at 14 weeks), in the early stages it should be approximately 1.5 cm, and by the end of the bearing the child should increase to 7.8 cm;
- measuring the circumference of the abdomen in a child - indicates the size of the embryo and its estimated weight;
- determination of the circumference of the head of the ripening fetus, which is also used to predict the natural birth of a child. Such a measurement is carried out even in the last stages of pregnancy, according to which the doctor looks at the size of the small pelvis of the future woman in labor and the head of the child. If the head circumference exceeds the parameters of the pelvis, then this is a direct indication for cesarean section.
Definition of malformations
With the help of ultrasound in the first weeks of pregnancy, various problems in the development of the baby and the possibility of curing him before birth are revealed. To do this, an additional consultation with a geneticist is prescribed, which compares the indicators and screening rates of the first trimester obtained during the examination.
Transcript of ultrasound may indicate the presence of any malformations of the child, but the final conclusion is given only after a biochemical study.
Screening of the 1st trimester, the norms for ultrasound: nasal bone
In an embryo with chromosomal abnormalities, ossification occurs later than in a healthy one. This can be seen as early as 11 weeks, when the first trimester is screened. Standards for ultrasound, the decoding of which will show whether there are deviations in the development of the nasal bone, help a specialist determine its value starting from 12 weeks.
If the length of this bone does not correspond to the gestational age, but all other indicators are in order, then there is no reason for concern. Most likely, these are the individual characteristics of the embryo.
The value of the coccyx-parietal size
An important indicator of the development of a little man at this stage of pregnancy is the size from the tailbone to the crown. If a woman has had irregular menstruation, this indicator determines the gestational age. The norm for screening ultrasound of the 1st trimester of this indicator is from 3.3 to 7.3 cm for a period of ten to twelve weeks inclusive.
The thickness of the space of the collar zone (TBP)
This indicator is also called the thickness of the cervical fold. It is noted that if the embryo's TBP is thicker than 3 mm, then there is a risk of Down syndrome in the child. The values used by the doctor are shown by screening of the 1st trimester. Standards for ultrasound (thickness of the collar space) are considered very important for further monitoring of a pregnant woman.
Determination of the location of the placenta
A child's place (placenta) is necessary for intrauterine blood supply to a small person. It is necessary to provide it with food. Ultrasound makes it possible to determine abnormalities of the development and position of the placenta. If it is located too low relative to the bottom of the uterus - this is called placenta previa, which can lead to overlapping exit for the baby during childbirth.
An ultrasound screening of the first trimester can show the location of the child's place well. The norms of such a study reject the low placenta previa. But even if it is located close to the bottom of the uterus, doctors are in no hurry to sound the alarm, since with the course of pregnancy it can rise. But if the position of the placenta has not changed in the later stages, then the following problems are possible:
- the placenta can obscure the cervix and prevent natural birth;
- since the lower part of the uterus is stretched in the second trimester , the placenta can exfoliate from it and cause severe bleeding (detachment of the placenta).
Yolk sac examination
On the 15-16th day of pregnancy from the day of conception, the process of formation of the yolk sac. This "temporary organ" of the baby is examined by ultrasound (1 trimester screening). Terms and standards for ultrasound examination should show its presence and size. If it has an irregular shape, is enlarged or reduced, then perhaps the fetus has stopped.
The yolk sac is an appendage located on the ventral side of the embryo. It contains a supply of yolk, necessary for the normal development of the baby. Therefore, to check what is the norm for screening ultrasound of the first trimester in comparison with the study parameters, it is very important for monitoring the course of pregnancy. Indeed, at first (until the child’s organs function independently), this appendage performs the function of the liver, spleen, and is also used as a supplier of primary germ cells, actively participating in the formation of immunity and in metabolic processes.
The role of biochemical blood analysis
Examining the condition of the embryo, the doctor looks not only at the results of ultrasound (screening of the 1st trimester). The norms in it are as important as in the analysis of blood. Such an analysis, in addition to ultrasound examination, is carried out to determine at what level specific proteins (placental) are located. The first screening is done in the form of a double test - to identify the level of 2 protein species:
- "PAPP-A" - the so-called pregnancy-related plasma protein A.
- "HCG" - the free beta subunit of human chorionic gonadotropin.
If the levels of these proteins are changed, then this indicates the possible presence of different chromosomal and nonchromosomal disorders. But identifying an increased risk does not mean that something is wrong with the embryo. Such results of screening for the first trimester, decoding, ultrasound norm indicate that you need to more closely monitor the progress of pregnancy. Often, repeated research no longer shows the risk of genetic diseases.