Without exaggeration, the expectation of a baby can be called the most reverent and exciting moment in the life of a future mother. And to make this expectation as cloudless as possible, the offer of prenatal examinations is enriched from year to year with more and more modern and affordable tests. How to navigate these proposals?
Non-invasive tests against invasive
The first thing a pregnant woman needs to know is that although non-invasive tests have quite informative characteristics, they give only a rough estimate of the risk of some chromosomal abnormalities, in particular trisomy 21 (Down syndrome), 13 or 18 and, possibly sex chromosome abnormalities. For this reason, non-invasive tests are considered screening, not diagnostic.
On the contrary, invasive tests allow you to determine the specific diagnosis, however, they also include the risk of spontaneous abortion. This risk is not high, but possible. Based on recent scientific studies, the risk of miscarriage is estimated at 1% for amniocentesis and 2% for villocentesis
So, on the one hand, safe tests for the fetus, but they only give a rough estimate, and on the other hand, diagnostic tests with a certain degree of risk. In order to make the right choice, a woman should get acquainted as early as possible (even before pregnancy) and be fully informed about the proposed studies. Thus, you will have enough time to think thoughtfully about it.
Ask yourself: «Ч“What exactly do I want to know about my baby before birth?” Keep in mind that under normal conditions, the risk of a sick baby is 3-4%. In 1% of cases, these are chromosomal abnormalities (the most important ones are 21, 13, 18, they account for 50 - 70% of the total number of pathologies), in other cases, there are malformations of the heart, kidneys, or skeleton.
You must be aware that all available prenatal examinations allow you to identify many of the above conditions, but not all of them. Faced with this situation, some patients automatically choose a test that gives more confidence regarding the health of the child (amniocentesis or villocentesis).
The expectant mother should have a clear understanding of the concept of prenatal diagnosis. Prenatal diagnosis is not needed to confirm that the baby is healthy. Its main task is to detect any problems.
The next question that is important to honestly answer yourself is: «What will I do if the test shows that the child has problems (or a high risk of problems)? » Avoiding the answer does not work, since the meaning of the prenatal diagnosis is precisely in making a decision regarding the future fate of the child. If there is a condition of the fetus that is considered unacceptable for parents, termination of pregnancy can be chosen, naturally, within the framework of the law.
If you know that no matter what happens, you have no intentions to terminate the pregnancy, then there is no need for screening tests that will create only unnecessary anxieties, all the more useless to do invasive diagnostics.
When to do?
Prenatal screening is performed between the eleventh and thirteenth weeks of pregnancy. If there is such a need for further research, amniocentesis (or villocentesis) is still available. If chromosomal abnormalities are confirmed, there is still the possibility of safe termination of pregnancy.
Occipital transparency (identified by the initials NT) is a collection of fluid visible through ultrasound in the form of a black space located behind the fetal neck. Between the eleventh and thirteenth weeks of pregnancy, all fetuses have this black space. However, in fetus with Down syndrome or other types of abnormalities, its thickness increases.
In addition to the aforementioned ultrasound, prenatal screening is combined with a specific maternal blood test. With chromosomal abnormalities, changes in the values associated with substances produced by the placenta are noted. In particular, these are ß-hCG free and PAPP-A. However, these values can be changed not only in the case of a chromosomal abnormality, but also in the presence of other variable factors (for example, in vitro fertilization).
Specialists of «Bogoliuby MC » will help you to understand the results of prenatal screening, as well as competently explain the feasibility of invasive diagnosis in case of a positive result. We remind you that these tests for prenatal screening do not have 100 per cent validity, and that they are positive only conditionally.