When do the first screening?
The first screening( first trimester screening) is a method of early detection of congenital malformations in the fetus. The first screening is carried out at a time not earlier than 10 and not later than 14 weeks of pregnancy( ideal is 12-13 weeks), since these terms are optimal for detecting gross developmental defects, as well as indicators of possible genetic abnormalities and diseases.
The first screening includes:
- Biochemical blood test. Two hormones are studied: beta-hCG( free b-subunit of human chorionic gonadotropin) and RAPP-A( pregnancy-associated protein A).
Ultrasound examination of
ultrasound allows to exclude or reveal congenital malformations of the fetus with a high degree of reliability. Its reliability can be affected by the uncomfortable position of the child, which does not allow to see everything that is necessary.
Basic stages of US
- Exclusion of ectopic pregnancy.
- Determination of the number of fruits.
- Determination of viability of the fetus. At 10 weeks, the fetus is already mobile, therefore, additional movements are tracked by the body and limbs. The beating heart of the child is clearly visible.
- Calculation of gestational age. To do this, determine the coccyx-parietal size - the maximum distance from the crown to its tailbone. According to the figure, the computer calculates the time.
- Inspection of fetal anatomy. Clearly visible head, limbs, trunk. In the head there is a rudiment of the brain, eye sockets, skull bones. In the trunk - the rudiments of the organs in the proper places, the normal exit of the umbilical cord. In the limbs - the correct location of large bones.
- Determination of the thickness of the collar space - skin folds on the neck of the fetus. Normally its value is up to 2 mm at 11 weeks and up to 3 mm at 14 weeks. Excess of this indicator can speak of genetic abnormalities in the fetus. An important indicator of the presence of hereditary diseases is a decrease in the size of the nasal bone relative to the term.
Biochemical blood test
Beta-hCG is a pregnancy hormone that is produced from its first weeks. It allows to reveal both pregnancy itself and chromosomal abnormalities.
Exceeding the norm of free beta-hCG on average doubles the risk of having a Down syndrome( trisomy 21) in the fetus, a decrease in the values of Edwards syndrome( trisomy 18).
RARP-A is a protein produced by the placenta. During pregnancy, his level rises, reaching a maximum for childbirth. The change in concentration allows us to judge the likely chromosomal abnormalities.
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