What Genetic Tests Are Taken During Pregnancy

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What Genetic Tests Are Taken During Pregnancy
What Genetic Tests Are Taken During Pregnancy

Video: What Genetic Tests Are Taken During Pregnancy

Video: Advanced prenatal genetic testing 2022, December

When the egg is fertilized, 23 chromosomes of the mother and 23 of the father are connected. Normally, the fetus should form 23 pairs of chromosomes, but sometimes, for various reasons, a failure occurs and in one link not 2, but 3 chromosomes are formed, which leads to a genetic disease of the fetus.

Genetic tests for pregnant women
Genetic tests for pregnant women


Step 1

The formation of three chromosomes instead of a pair is called trisomy. The formation of trisomy at locus 21 leads to the development of Down syndrome in the fetus, with the formation of characteristic facial features and underdeveloped intelligence. When trisomy is formed on chromosome 16, neural tube defects develop, i.e. the embryo does not form a bone around the spinal cord or brain. Such children cannot live long, because they do not have a skull or spinal column that protects sensitive axons and dendrites. The origin of three chromosomes at locus 18 leads to the development of Edwards syndrome, which is characterized by a very small neck size, an unusual head shape with low-set ears and weak intelligence.

Step 2

The likelihood of the risk of developing fetal genetic abnormalities is higher in mothers over 35 years old. Also at increased risk are women who abuse alcoholic beverages, smoke or with drug addiction. Chronic intoxication, for example, work in harmful working conditions, etc., can affect the development of trisomy.

Step 3

The likelihood of a fetus having trisomies can be determined with a specific blood test already in the first trimester of pregnancy. According to the federal program "Children of Russia", every pregnant woman can undergo perinatal screening for genetic abnormalities of the fetus during the period of 16-18 weeks of pregnancy. There are other screening tests, for example, the Invitro laboratory conducts the PRISCA 1 test at 11-13 weeks of pregnancy and PRISCA 2 at 16-18 weeks of pregnancy, in which the risk of developing genetic diseases is determined by blood.

Step 4

The screening results show only the likelihood of developing a gene pathology; with high rates, a woman is at risk. To confirm the diagnosis of congenital fetal pathology, use the procedure for taking amniotic fluid for analysis, i.e. perform amniocentesis. The study of amniotic fluid with great accuracy allows us to make a conclusion about the presence or absence of congenital trisomy in the fetus.

Step 5

With questionable results with amniocentesis, another specific procedure is used - taking placenta cells or blood from the umbilical cord for genetic analysis. Prenatal karyotyping of the fetus is carried out with the help of the smallest puncture of the amniotic fluid; material is taken under ultrasound control. The placenta, like the fetus, develops from a fertilized egg, so they have the same DNA. If genetic changes are observed in the chromosome set of the placental cell, it means that the fetus also has trisomies or other disruptions in the DNA code, which lead to severe congenital malformations.

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