The norm for screening ultrasound is 1 trimester. Screening for 1 trimester: timing, ultrasound, decoding of ultrasound

With the onset of pregnancy, a woman starts to worry about a lot of questions. Each future mother wishes her baby a normal formation and development. In the early stages, there may be risks of developing certain diseases of the embryo. To study the condition of the baby, doctors prescribe a screening for the first trimester. Norms for ultrasound (a photo of the survey is usually attached), a woman can find out from a specialist who watches her.

What is perinatal screening?

Perinatal screening implies the study of a pregnant woman, which allows to identify various defects of the child at the stage of intrauterine development. This method includes two types of examination: a biochemical blood test and ultrasound examination.

The optimal time for conducting such a survey is determined - this period is from ten weeks and six days to thirteen weeks and six days. There is a certain norm for screening ultrasound of 1 trimester, which compares the results of a survey of a pregnant woman. 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:

• The size of the TVP - the thickness of the space of the collar zone;
• Underdevelopment or absence of the bones of the nose.

Ultrasound in pregnancy can reveal signs of such a disease as Down's syndrome, and some more pathologies of fetal development. Norm for screening (ultrasound) 1 trimester should be analyzed up to 14 weeks. Later this period, many indicators are not yet informative.

Screening for 1 trimester: ultrasound guidelines (table)

To a doctor it was easier to determine the condition of a pregnant woman, there are certain tables of indicators of development of the baby's organs. The very protocol of ultrasound research is structured in order to understand the dynamics of the formation and growth of the embryo. The article presents the norms of screening for the first trimester.

Decoding of ultrasound (the table is shown below) will help to get information about whether everything is in order with the fetus.

Determination of viability of the embryo

To assess the viability of the embryo is very important to look at the heartbeat in the early stages. In a small person, the heart begins to beat as early as the fifth week of being in the womb of the mother, and it is possible to identify it using the first trimester screening (ultrasound norms), starting from the seven weeks of the fetus's life. If at this time palpitation is not found, we can talk about the probability of fetal death (a dead pregnancy).

To assess the viability of the embryo, another HR is taken into account, which is normal for a period of six weeks from 90 to 100 beats per minute. These important indicators of 1 trimester screening, ultrasound norms along with the study of blood flow and body length should correspond to the reference data on the duration of pregnancy.

The more modern equipment used for examination, the better you can see all the organs and get the most accurate results. If there is a high probability of the presence of congenital malformations or genetic abnormalities of development, the pregnant woman is sent to a deeper examination.

In some regions, when registering with a women's consultation, it is mandatory for all pregnant women to screen for 1 trimester. Norms on ultrasound may not coincide with the results, so 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 a survey: they are women of thirty-five years old, those who have genetic diseases in the family and those born earlier have had miscarriages in previous pregnancies, stillbirths or an undeveloped pregnancy. Careful attention is also given to future mothers who have experienced viral diseases at the beginning of pregnancy, who take dangerous medicines or are exposed to radiation.

If a woman has spotting in the first trimester, ultrasound can reveal the degree of viability of the child or his death.

Pregnancy Time

An additional examination to determine the exact period of the pregnancy status is indicated for women who have an irregular menstrual cycle or who do not even know about the date of conception of the child. For this, in most cases, screening is used for the first trimester. Norms on ultrasound, the decoding of the main indicators and the date of conception do not require special medical knowledge. A woman herself can see the expected date of delivery, the length of pregnancy and the number of embryos. Basically, the number of weeks, determined by ultrasound, corresponds to the time that is calculated from the first day of the female cycle.

During the study, the doctor makes control measurements of the size of the embryo. With the data obtained, the specialist compares the screening norms for the first trimester. The decoding of ultrasound occurs according to the following parameters:

• Measurement of the distance between the sacrum and the embryo's embryo (7-13 weeks), which makes it possible to determine the actual duration of pregnancy according to special tables;
• Measuring the length of the parietal bone of the head of a future child (after 13 weeks), this is an important indicator in the second half of pregnancy;
• Determining the size of the longest - the femoral body of the embryo, its indicators reflect the growth of the child in length (at 14 weeks), in early terms it should be about 1.5 cm, and by the end of the bearing the child will increase to 7.8 cm;
• Measuring the abdominal circumference in the child - indicates the size of the embryo and its estimated weight;
• Determination of the length of the head circumference of a maturing fetus, which is also used to predict the natural birth of a child. This measurement is carried out even at the last stages of pregnancy, according to which the doctor looks at the size of the small pelvis of the future mother and baby's head. If the head circumference exceeds the parameters of the pelvis, then this is a direct indication for the caesarean section.

Identification of malformations

With the help of ultrasound in the first weeks of pregnancy, various problems in the development of the child and the possibility to cure it before birth are revealed. To do this, an additional consultation of a geneticist is made, which compares the results obtained during the survey and the norms of screening for the first trimester.

The decipherment of ultrasound may indicate the presence of any malformations of the child, but the final conclusion is given only after a biochemical study.

Screening for 1 trimester, ultrasound guidelines: nasal bone

In an embryo that has chromosomal abnormalities, ossification occurs later than in a healthy one. This can be seen as early as 11 weeks, when 1 trimester is screened. Norms on ultrasound, the decoding of which will show whether there are deviations in the development of the nasal bone, help the specialist to determine its value from 12 weeks.

If the length of this bone does not match the duration of pregnancy, but all other indicators are in order, then there is no reason for concern. Most likely, these are individual features of the embryo.

Value of coccygeal-parietal size

An important indicator of the development of a small man in this period of pregnancy is the size from the coccyx to the crown. If a woman had irregular menstruation, this indicator determines the duration of pregnancy. The norm for screening ultrasound of the first 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 (TVP)

This indicator is also called the thickness of the cervical fold. It is noted that if the TVP of the embryo is thicker than 3 mm, then there is a risk of Down's syndrome in the child. The values that the doctor uses show the screening of the first trimester. Standards for ultrasound (thickness of the collar space) are considered very important for the further monitoring of the pregnant woman.

Determining the location of the placenta

A child's place (placenta) is necessary for the intrauterine blood supply of a small person. It is needed to provide it with food. Ultrasound gives an opportunity to determine anomalies in the development and position of the placenta. If it is too low relative to the uterine fundus - this is called placenta previa, which can lead to overlapping of the exit for the child during childbirth.

It is good to show the location of a child's place can ultrasound screening for 1 trimester. The norms of this study reject a low placenta previa. But even if it is located close to the bottom of the uterus, doctors are not in a hurry to sound the alarm, as with the course of pregnancy it can rise. But if the position of the placenta has not changed at a later date, then the following problems are possible:

• The placenta may obscure the cervix and prevent natural childbirth;
• Since in the second trimester the lower part of the uterus stretches, the placenta can peel off from it and cause severe bleeding (exfoliation of the placenta).

Study of the yolk sac

On the 15-16th day of pregnancy from the day of conception, the process of formation of the yolk sac proceeds . This "temporary organ" of the baby is examined by doing ultrasound (1 trimester screening). Terms and standards for ultrasound examination should show its availability and dimensions. If it is irregularly shaped, enlarged or reduced, then the fetus may have frozen.

The yolk sac is an appendage that is on the ventral side of the embryo. It contains a supply of yolk, necessary for normal development of the baby. Therefore, to check which norm for screening ultrasound of 1 trimester in comparison with the parameters of the study is very important for monitoring the course of pregnancy. After all, at first (while the child's organs do not function independently), this appendage performs the function of the liver, spleen, and is also used as a supplier of primary sex cells, actively involved in the formation of immunity and in metabolic processes.

Role of biochemical blood test

Investigating the state of the embryo, the doctor looks not only at the results of ultrasound (1 trimester screening). Norms in it are important the same as in the analysis of blood. Such an analysis in addition to the ultrasound examination is carried out to determine the level at which 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:

1. "RAPP-A" - the so-called pregnancy-associated plasma protein A.
2. "HCG" - a free beta subunit of human chorionic gonadotropin.

If the levels of these proteins are changed, this indicates the possible presence of different chromosomal and nonchromosomal abnormalities. But identifying an increased risk does not mean that there is something wrong with the embryo. Such results of screening of the first trimester, decoding, the norm of ultrasound indicate that it is necessary to observe more carefully the course of pregnancy. Often repeated research no longer shows the risk of genetic diseases.