Each married couple dreams of giving birth to a strong and healthy baby. But, to our great regret, no one is immune from the fact that the development of a child can go with problems due to genetic abnormalities.
During pregnancy, the expectant mother passes tests, undergoes many different studies, as well as monitoring fetal development and preparation for childbirth. But, despite all this, children with Down syndrome are constantly born in the country. Naturally, each such case is an incredible grief and a complete surprise for parents.
This is due to the fact that a conventional ultrasound study cannot determine this syndrome and other chromosomal abnormalities. For example, using ultrasound, you can evaluate only the external data of the baby and identify certain congenital malformations in the development. But now, most of the children born with Down and Edwards syndrome do not have any external abnormalities. It is possible to determine with accuracy that the fetus has a chromosomal disorder, but only after conducting combined genetic screening is a complex of measures and studies. They are carried out before delivery.
Screening - what is it?
The word means "sifting," if translated from English. Ultrasound screening is carried out for almost all expectant mothers, even if the pregnancy is absolutely normal. Do it from 11-13 weeks of pregnancy.
Combined genetic screening is a series of activities that are carried out before delivery and are aimed at diagnosing genetic abnormalities. It includes ultrasound and biochemical examination, as well as an individual calculation of the risk of carrying a child with a chromosomal pathology.
It is important to note that the results of such a study cannot be called the basis for a diagnosis. After all, screening is just an opportunity to establish the degree of risk of a chromosomal disease. If it is high, invasive cytogenetic studies are prescribed for expectant mothers.
How are pregnant women screened? Let's consider in more detail
The first stage of the screening procedure is an ultrasound examination of the fetus. In the course of it, the correspondence of the size of the baby to the gestation period, the general condition of the embryo, some expressed malformations in development, etc. That is, what can be seen externally. But it is worth noting that even if there are no visible pathologies, this does not mean that they are not there.
For example, in babies suffering from Down syndrome, only in half the cases can visual defects be noticed.
A more accurate result of the presence of chromosomal diseases can be obtained only after the second screening stage, the biochemical one, has passed. Here, the blood of the expectant mother is examined for the presence of a specific substance that is secreted by the placenta. The ratio and concentration in the blood of specific proteins and marker substances are also evaluated.
The third stage is the calculation of the risk of obtaining chromosomal pathologies using special computer programs. In addition to previous results, indicators such as maternal age and weight, gestational age, bad habits, genetic diseases, and even ethnicity are also used. After the computer processes the received information, the doctor can conclude how high the risk of having a child with genetic diseases.
If it is at a low level, the patient eliminates the need to re-pass any studies, she is usually monitored. When the level is average, another screening is performed in the second trimester. When the risk is high, a prenatal diagnostic program is prescribed . It already with an accuracy of 100% can determine the presence of any chromosomal abnormalities.