Screening for the first trimester, what can the result tell?
Now during pregnancy, a woman does a lot of research. One of them is the screening of 1 trimester, which allows you to suspect serious pathologies of the fetus and pregnancy. However, a woman needs to understand that the results of this study are not a verdict.
Therefore, if the result of screening for Down's syndrome is positive, do not despair and get upset. This does not mean that the baby is necessarily born with this pathology, but the probability is higher than that of others.
Screening for the first trimester includes ultrasound and the so-called "double test".The optimal time for it is the period from 10 to 13 weeks. First, you need to make an ultrasound to determine the number of fruits, their size, the length of pregnancy.
And then a biochemical screening of the 1 trimester is carried out, which consists of analyzes on RAPP-A and b-hCG.The concentration of these markers in the blood of a future mother in combination with ultrasound data makes it possible to reveal the probability of chromosomal abnormalities in a baby.
In order for the result to be reliable, it is necessary to indicate weight, age, ethnicity, and whether the woman suffers from diabetes and smokes. If the baby was conceived with IVF, then it should also be noted.
1 trimester screening is performed to assess the likelihood of a baby having Edwards syndrome, Down's syndrome, neural tube defect. Indications for its conduct are:
- harmful effects on parents, for example, irradiation;
- female over 35;
- hereditary diseases in relatives;
- the presence of a child with chromosomal abnormalities and malformations, including the fetus with interrupted pregnancy.
However, today gynecologists recommend to pass this study to absolutely all pregnant women. In addition, in many women's clinics it is held absolutely free of charge.
Today, often correct the reference values, taking into account individual data. The MoM calculation is used to analyze the results. This is the ratio of the data obtained in the study to the individual median values.
Such an integrated approach increases the reliability of screening. It helps to determine Down syndrome in 1 trimester in 90% of cases, however, while 5% of the results are false positive. Also, the reliability of the study may affect the intake of certain drugs, especially hormones.
In addition, the decrease and increase in the level of PAPP-A and b-hCG may occur in conditions that are not associated with chromosomal abnormalities. Among them, intrauterine infections, mother's diseases, obstetric complications.
The results should be analyzed by a qualified technician. Nevertheless, looking at them some assumptions, it can be done not by a doctor.
According to the results of ultrasound, the thickness of the collar area should not be more than the norm of 2.6 mm. The nasal bone of the fetus at this time should be visualized, otherwise there is a risk of chromosomal abnormalities.
The normal concentration of b-hCG lies in the range of 14.3-130.5 ng / ml. If it is less, then there is a risk that the fetus has Edwards syndrome, especially if the level of RAPP-A is also low.
If the concentration is more than 2 times higher than normal, then you can suspect Down's syndrome in the baby. Especially if the concentration of PAPP-A is lower than required and the results of ultrasound are not comforting. Extremely low values of these markers may indicate the arrest of fetal development.
At a PAPP-A level, Shereshevsky-Turner syndromes, Corneli de Lange, may be less than normal. In addition, defects in implantation of the embryo and formation of the placenta are possible, which will manifest later.
These pathologies can lead to hypertensive complications, nephropathy, premature birth, frozen pregnancy, fetal hypoxia. Such women should be monitored, additional research and therapy are needed.
The corrected MoM values are also important. They should be above 0.6 and less than 2. Pregnancy requires monitoring with MOP over PAPP-A below 0.5.
Thus, 1 trimester screening is an important study that allows to identify chromosomal abnormalities in the fetus, as well as possible pathologies of pregnancy. It consists of the ultrasound that is performed first, and analyzes on RAPP-A and b-hCG.The results of the study are not a definitive diagnosis, but only an estimate of probability.