The first screening examination is prescribed to detect fetal malformations, analyze the location and blood flow of the placenta, and also to determine the presence of genetic abnormalities. Ultrasound screening of the first trimester is carried out in a period of 10-14 weeks solely as directed by a doctor.
What is an ultrasound in the first trimester?
Ultrasound is performed in specially equipped private clinics or women's clinics, in which there are relevant professionals who are able to conduct the necessary diagnostics.
Ultrasound screening of the first trimester will help to conduct a full examination at a short gestational age. How the study is conducted, the attending physician will explain, and if necessary, he will tell you how to prepare for the diagnosis.
A screening study is carried out in a transabdominal manner (through the abdominal wall) using an ultrasound diagnostic apparatus. In the final ultrasound protocol, the following indicators are indicated:
- structural features of the uterus and appendages;
- visualization of the fetus and yolk sac;
- the location and structure of the chorion;
- fetal heart rate;
- the size of the fetus from the toe to the coccyx;
- thickness of the cervical fold.
An ultrasound specialist will be able to determine the exact gestational age, exclude any genetic pathologies and fetal malformations, and also see if there are pathologies in the reproductive system of women that can complicate the course of pregnancy or cause its termination. Ultrasound screening of the 1st trimester provides a full examination of the pregnant woman and the fetus according to all necessary parameters.
Decoding of the main parameters of ultrasound
Before starting the diagnosis, the doctor should clarify the start date of the last menstruation in order to be able to check the conformity of the size of the fetus with the gestation period. Decryption is carried out directly by a doctor who understands all terminology and knows the norms of fetal development.
The most important indicators of the first screening are the heart rate and the coccygeal-parietal size of the fetus. ChES in the period from 10 to 14 weeks can vary between 150-175 beats / minute.
The size of the fetus from the toe to the coccyx in a period of 13 weeks should be at least 45 mm. Ultrasound screening of the 1st trimester must be carried out up to 13 weeks 6 days, since in the future it will be difficult to determine the compliance of the fetal parameters with the accepted standards.
Decoding of additional parameters of ultrasound
The presence of chromosomal abnormalities of the fetus is determined by the thickness of the collar space. This indicator allows you to determine only the screening of 1 trimester. How do ultrasounds, you can find on the Internet or ask your doctor.
Analysis of the structure and location of the chorion allows you to determine the future placement of the placenta, to determine how pregnancy develops. It is important to note that if the chorion is attached near the internal pharynx of the uterus, then there is a chance of developing placenta previa.
The yolk sac by the 12th week is almost completely neutralized, since by this time the placenta begins to ripen, which will perform all the same functions and provide the fetus with nutrients and all the factors necessary for normal development.
Analysis of the condition of the female genital organs is also very important. Since the non-standard form of the uterus (saddle, bicorn) can cause a termination of pregnancy or fetal freezing. Appendages are also examined for cysts. In some cases, during pregnancy, there is a need for surgical intervention to eliminate the pathology.
To describe the pathologies found, the uzist doctor writes a comment at the end of the protocol. Ultrasound screening of the first trimester is a very important examination, which allows to fully identify all possible pathologies and abnormalities of the development of the fetus and genitals of the pregnant woman.
Features of preparation for ultrasound
Before the procedure, special diets or bowel cleansing are not required. A woman only needs to bring a towel and a disposable diaper to her ultrasound room. When you first visit the ultrasound room, you need to wait for a slight filling of the bladder.
An experienced doctor will be able to timely detect any, even minor problem and effectively eliminate it without harming either the developing fetus or the health of the mother.
How to determine Down syndrome by ultrasound?
The cervical fold in the period of 11-13 weeks should not exceed 3 mm. Decryption of ultrasound screening of the 1st trimester should be carried out only by the attending physician, who knows about all the individual characteristics of the body.
In addition to the thickness of the collar space, the presence of Down syndrome can be determined by such factors as:
- lack of a nasal bone;
- impaired blood flow in the venous duct;
- the presence of tachycardia (heart palpitations);
- reduction in the size of the maxillary bone;
- enlarged bladder size;
- the absence of a second umbilical artery (normally there should be two umbilical arteries providing the fetus with proper blood flow and a sufficient amount of oxygen and nutrients).
It should be noted that some indicators can also occur in healthy children. This is especially true for the presence of the nasal bone, which is absent at 11 weeks in approximately 2% of children. Blood flow disturbance occurs in 5% of healthy children and is not a pathology requiring medical intervention.
It is necessary to carefully analyze the results of screening 1 trimester. Ultrasound is not in all cases able to show a complete picture of the development of the child.
Preparation for biochemical screening
Before blood sampling from a vein, it is necessary to adhere to a certain diet the day before the examination and exclude:
- chocolate;
- seafood;
- fatty foods;
- meat products.
Within 4 hours before blood sampling, you must completely refuse to eat. This will give the most accurate result.
1st trimester screening: ultrasound and blood as indicators of fetal health
In the first trimester, there is a need to conduct not only an ultrasound examination, but also it is necessary to examine blood from a vein, which determines the level of hCG and PAPP-A.
When diagnosing blood, not only the total hCG is determined, but also its free β-subunit. Normally, this indicator in any laboratory should be in the range of 0.5-2 MoM. In violation of the norms, the risk of the manifestation of the Down syndrome in the fetus, or various chromosomal abnormalities, is significantly increased.
An increase in the free β-subunit of hCG indicates the presence of Down syndrome in the fetus. While a decrease in the concentration of this indicator increases the risk of a child developing Edwards syndrome.
PAPP-A is a plasma protein A associated with pregnancy. A proportional increase in this indicator indicates the normal course of pregnancy. Deviation from the norm indicates the presence of pathologies of the fetus. However, this only applies to lowering the concentration of the indicator in the blood below 0.5 MoM, exceeding the norm by more than 2 MoM does not pose any danger to the development of the baby.
1st trimester screening: transcript of ultrasound results and a test for the risk of pathologies
In laboratories there are special computer programs that, in the presence of individual indicators, calculate the risk of developing chromosomal diseases. Individual indicators include:
- age;
- weight;
- the presence of bad habits;
- chronic or pathological diseases of the mother.
After entering all the indicators in the program, she will calculate the average RAPP and hCG for a specific gestational age and calculate the risk of anomalies. For example, a ratio of 1: 200 indicates that in a woman out of 200 pregnancies, 1 child will have chromosomal abnormalities, and 199 children will be born completely healthy.
A negative test indicates a low risk of developing Down syndrome in the fetus and does not require any additional tests. The next examination for such a woman will be an ultrasound in the second trimester.
Depending on the ratio obtained, a conclusion is given in the laboratory. It can be positive or negative. A positive test indicates a high probability of having a baby with Down syndrome, after which the doctor prescribes additional studies (amniocentesis and chorionic villus sampling) to make a final diagnosis.
Ultrasound screening of the 1st trimester, reviews of which allow a woman to better understand the results, is not always worth taking seriously, because only a doctor can correctly decrypt the protocol.
What should be done with a high risk of developing Down syndrome?
If you find a high risk of giving birth to an unhealthy baby, you should not immediately resort to extreme measures to terminate the pregnancy. Initially, it is necessary to visit a genetics doctor who will conduct all the necessary studies and determine exactly if there is a danger of a child developing chromosomal abnormalities.
In most cases, a genetic examination refutes the presence of problems in the child and therefore the pregnant woman can safely bear and give birth to a child. If the examination confirms the presence of Down syndrome, then the parents must independently decide whether to keep them pregnant or not.
What indicators can affect the results?
When a woman is fertilized by IVF, the indicators may differ. The concentration of hCG will be exceeded, at the same time, PAPP-A will be reduced by approximately 15%, an ultrasound examination may show an increase in LZR.
Weight problems also greatly affect hormone levels. With the development of obesity, the level of hormones increases significantly, if the body weight is excessively low, the hormones will also be reduced.
The worries of the pregnant woman associated with worries about the correct development of the fetus can also affect the results. Therefore, a woman should not pre-configure herself in the negative.
Can a doctor insist on abortion if a fetal Down syndrome is detected?
No doctor can force an abortion. The decision to keep the pregnancy or to terminate it can only be made by the baby's parents. Therefore, it is necessary to carefully think over this issue and determine the pros and cons of giving birth to a child with Down syndrome.
Many laboratories allow you to see a three-dimensional picture of the development of the child. A photo of an ultrasound screening of the 1st trimester allows parents to forever keep the memory of the development of their long-awaited baby.