Ultrasound screening for 1 trimester: interpretation of the results
The first screening examination is assigned to detect fetal malformations, analyze the location and blood flow of the placenta, and to determine the presence of genetic abnormalities. Ultrasound screening for the first trimester is carried out at a period of 10-14 weeks, exclusively for the doctor's prescription.
What is ultrasound in the first trimester?
The ultrasound is carried out in specially equipped private clinics or women's clinics, in which there are appropriate professionals able to conduct the necessary diagnostics.
To conduct a full-fledged examination at a small pregnancy period will help ultrasound screening for 1 trimester. As the research is carried out, the attending physician will explain, and if necessary he will tell you how to prepare for the diagnosis.
The screening test is performed in a transabdominal way (through the abdominal wall) using an ultrasound diagnostic device. In the final ultrasound protocol, the following indicators are indicated:
- features of the structure of the uterus and appendages;
- visualization of fetus and yolk sac;
- location and structure of the chorion;
- frequency of fetal heart contractions;
- the size of the fetus from the crown to the tailbone;
- thickness of the cervical fold.
An ultrasound specialist will be able to determine the exact duration of pregnancy, exclude any genetic pathologies and malformations of the fetus, and also see if there are pathologies in the sexual system of the woman that can complicate the course of pregnancy or cause its interruption. Ultrasound screening of 1 trimester provides a full examination of the pregnant and fetus on all necessary parameters.
Explanation of the basic parameters of ultrasound
Before starting the diagnosis, the doctor should specify the date of the last menstruation, in order to be able to check the conformity of the fetus size to the term of pregnancy. 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 frequency of cardiac contractions and the coccygeal-parietal fetal size. ChS in the period from 10 to 14 weeks can vary between 150-175 beats / minute.
The fetal size from the crown to the coccyx in a period of 13 weeks should be at least 45 mm. Ultrasound screening for 1 trimester must be performed up to 13 weeks 6 days, as it will be difficult in future to determine the compliance of the fetal parameters with the accepted standards.
Explanation of additional parameters of ultrasound
The presence of chromosomal abnormalities of fetal development is determined by the index of the thickness of the collar space. This indicator allows you to determine only the screening of the first trimester. How do ultrasound, 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 location of the placenta, determine how the pregnancy is developing. It is important to note that if the chorion is attached near the inner throat of the uterus, then there is a possibility 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 genitalia is also very important. Since the non-standard form of the uterus (saddle, bicorn) can cause interruption of pregnancy or fading of the fetus. Attachments are also examined for cysts. In some cases, during pregnancy, there is a need for an operative intervention to eliminate pathology.
To describe the found pathologies, the doctor-ultrasound enters the comment at the end of the protocol. Ultrasound screening of the first trimester is a very important survey that allows to fully identify all possible pathologies and abnormalities of the fetus and genitalia of the pregnant woman.
Features of preparation for the conduct of ultrasound
The procedure does not require special diets or bowel cleansing. A woman only needs to bring a towel and a disposable diaper to her office with her. When you first visit the ultrasound room, you need to wait for a small filling of the bladder.
An experienced physician 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 on ultrasound to determine Down's syndrome?
Cervical fold in the period of 11-13 weeks should not exceed 3 mm. The transcript of ultrasound screening for the first trimester should only be performed by the attending physician, who knows about all the individual characteristics of the organism.
In addition to the thickness of the collar space, the presence of Down's syndrome can be determined by factors such as:
- absence of nasal bones;
- violation of blood flow in the venous duct;
- presence of tachycardia (rapid heartbeat);
- reduction of the size of the maxillary bone;
- increased size of the bladder;
- absence of the second umbilical artery (normally there should be two umbilical arteries, which ensure the fetus has the proper blood flow and a sufficient amount of oxygen and nutrients).
It should be noted that some indicators can also be found in healthy children. Especially it concerns the presence of a nasal bone, which is absent in the period of 11 weeks in about 2% of children. Violation of the blood flow occurs in 5% of healthy children and is not a pathology requiring medication.
It is necessary to carefully analyze the results of screening for the first trimester. Ultrasound can not in all cases show a complete picture of the child's development.
Preparation for biochemical screening
Before taking blood from the vein, you need to adhere to a certain diet the day before the examination and exclude:
For 4 hours before taking blood, you must completely stop eating. This will give the most accurate result.
1 trimester screening: ultrasound and blood as indicators of fetal health
In the first three-place there is a need for not only an ultrasound, but it is also necessary to examine the blood from the vein, which determines the level of hCG and RAPP-A.
In the diagnosis of blood, not only the total hCG, but also its free β-subunit is determined. Normally, this indicator in any laboratory should be in the range of 0.5-2 MW. If the norms are violated, the risk of manifestation in the fetus of Down syndrome, or various chromosomal abnormalities, is significantly increased.
An increase in the free β-subunit of HCG indicates a possible fetal Down syndrome. While a decrease in the concentration of this indicator increases the risk of developing a child's syndrome Edwards.
RAPP-A is plasma protein A, associated with pregnancy. A proportional increase in this indicator indicates normal pregnancy. Deviation from the norm indicates the presence of pathologies of fetal development. However, this only applies to a decrease in the concentration of the indicator in the blood of less than 0.5MoM, exceeding the norm of more than 2 MoM does not pose any dangers for the development of the baby.
Screening for the first trimester: deciphering the results of ultrasound and a test for the risk of developing pathologies
In the laboratories there are special computer programs that, in the presence of individual indicators, calculate the risk of developing chromosomal diseases. Individual indicators include:
- the 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 pregnancy and calculate the risk of anomalies. For example, the ratio 1: 200 indicates that a woman of 200 pregnancies will have 1 child with chromosomal abnormalities, and 199 children will be born completely healthy.
A negative test indicates a low risk of developing in the fetus of Down syndrome and does not require any additional tests. The next examination for such a woman will be ultrasound in the second trimester.
Depending on the obtained ratio, 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's syndrome, after which the doctor prescribes additional studies (amniocentesis and chorionic villus sampling) to make a final diagnosis.
Ultrasound screening of the first trimester, which allows a woman to understand more of the results obtained, is not always worth taking seriously, because only the doctor can correctly decrypt the protocol.
What should be done with a high risk of Down syndrome?
If you find a high risk of giving birth to an unhealthy child, do not immediately resort to extreme measures to interrupt pregnancy. Initially, it is necessary to visit a genetics physician who will conduct all necessary studies and determine exactly whether there is a danger of a child developing chromosomal abnormalities.
In most cases, genetic examination refutes the presence of problems in the child and therefore a pregnant woman can calmly bear and give birth to a child. If the examination confirms the presence of Down's syndrome, then the parents must decide on their own whether to keep them pregnant or not.
What indicators can affect the results?
When a woman is fertilized by IVF, the indicators may differ. Concentration of hCG will be exceeded, while PAPP-A will be reduced by approximately 15%, with ultrasound examination, an increase in LDD can be detected.
Problems with weight also strongly affect the hormones. With the development of obesity, the level of hormones increases significantly, if the body weight is too low, hormones will also be reduced.
Excitement of a pregnant woman, associated with experiences about the correctness of the development of the fetus, can also affect the results. Therefore, a woman should not pre-adjust herself to the negative.
Can the doctor insist on an abortion if Down syndrome is found in the fetus?
No doctor can force you to interrupt your pregnancy. The decision to keep the pregnancy or its interruption can be made only by the parents of the baby. Therefore, it is necessary to think carefully this question and determine all the pros and cons of the birth of a child with Down syndrome.
Many laboratories allow you to see a three-dimensional picture of a child's development. Photo ultrasound screening 1 trimester gives parents the opportunity to permanently preserve the memory of the development of their long-awaited baby.