Prenatal diagnosis is a complex of studies that allows detecting genetic abnormalities and pathologies of the development of the embryo during the gestational period. Prenatal diagnosis allows to make a reasoned decision to terminate a pregnancy for medical reasons or to develop a strategy for restoring the health of the future child. Prenatal screening allows to predict with great reliability the health of a child conceived in a family with hereditary pathologies
Prenatal diagnosis is a relatively young area of medicine that is developing rapidly. Modern methods are used for research:
Prenatal screening is recommended to be performed in the I and II trimesters of pregnancy - during the period when it is possible to terminate the pregnancy without consequences for the woman. Prenatal diagnosis of hereditary diseases allows to establish the presence of all chromosomal syndromes and more than 100 genetically determined pathologies with great reliability.
Biochemical screening during pregnancy is indicated to determine:
For research in the I and II trimesters of pregnancy, a blood sample is taken from a pregnant woman. Using a computer system, the probability of the development of chromosomal mutations and genetically determined diseases is calculated based on the results of the detection of markers, ultrasound results and other indicators.
Biochemical screening is also carried out to clarify the degree of intrauterine disorders of the development of the lungs and heart of the fetus, the degree of expression of the Rhesus conflict, detection and assessment of the severity of hypoxia.
The First Trimester Screen of the of pregnancy is performed at the 11th or 13th week of pregnancy. Before 11 weeks of pregnancy, it makes no sense to perform the research, because the results obtained will be unreliable.
The First Trimester Screen includes ultrasound and biochemical screening. Some women, being at-risk group, go for research at the 10th week of pregnancy, but experts believe that this is too short a period which can show unreliable results. Ultrasound of the fetus in the first trimester determines:
Ultrasound is performed by transabdominal and transvaginal methods. At the 12th week of pregnancy, a venous blood sample is taken for biochemical studies. It is determined the amount:
Based on the listed screening results, the risk of hereditary diseases is calculated. If the result is positive, then in the second trimester invasive studies are performed, based on the results of which a conclusion is made about the need to terminate or prolong the pregnancy.
If the fetus has a risk of limb reduction, then a woman is prescribed an ultrasound at 14 weeks of pregnancy.
The Second Trimester Screening is done at 17th-19th weeks of pregnancy. The data obtained in this gestational period are the most informative. If the data obtained during the first screening are normal, then the woman is prescribed only ultrasound.
If congenital pathologies are suspected, a full examination is prescribed. In this case, the second trimester screening includes invasive research methods. By a fetal tissue biopsy it is determined the presence of:
Biopsy is the most traumatic research method. The biopsy sample is taken under the visual control of an ultrasound machine or a fetoscope.
Invasive research methods include umbilical cord blood analysis and cellular composition of amniotic fluid. If needed, the chorion villi and placenta are examined. Material is collected under ultrasound control. Material is collected under ultrasound control.
Fetoscopy is a visual examination of the fetus using a flexible tube with an optical system, which is carried out only according to indications from the 18th week of pregnancy to the 23rd week.
In the II trimester, the fetometry of the fetus is carried out using ultrasound. It shows the correspondence of the anatomical development of the fetus to the reference value and its position in the uterus, the thickness and structure of the child's place, the umbilical cord parameters, internal organs formation.
If pathologies are detected timely, there is an possibility to plan effective treatment.