Screening of 1 trimester - interpretation of the results

What does the trimester screening show? This ultrasound examination, which helps determine the possible presence of chromosomal diseases in the early stages of pregnancy. During this period, women should also undergo a blood test for hCG and RAPP-A. If it turns out that the results of screening for the first trimester are bad (ultrasound and blood counts), this indicates a high risk of Down's syndrome in the fetus.

Norms of screening for the first trimester and their interpretation

During ultrasound, the thickness of the cervical fold in the fetus is examined, which should increase proportionally as it grows. The examination is carried out on the 11-12th week of pregnancy, and the cervical fold should be 1 to 2 mm at this time. By week 13, it should reach a size of 2-2.8 mm.

The second of the indicators of the norm of screening for the first trimester is the visualization of the nasal bone. If it is not visible during the examination, this indicates a risk of Down syndrome in 60-80%, but it is considered that in 2% of healthy fetuses, it can also not be visualized at this time. By 12-13 weeks the norm of the size of the nasal bone is about 3 mm.

In the course of ultrasound at 12 weeks determine the age and approximate date of birth of the child.

Screening for the first trimester - deciphering the results of blood tests

The biochemical analysis of blood on beta-hCG and RAPP-A is deciphered by transferring the indices into a special MoM value. The obtained data indicate the presence of abnormalities or their absence for a given period of pregnancy. But these factors can affect different factors: the age and weight of the mother, lifestyle and bad habits. Therefore, for a more accurate result, all data is entered into a special computer program, taking into account the personal characteristics of the future mother. Results of the degree of risk this program shows in the ratio 1:25, 1: 100, 1: 2000, etc. If you take, for example, option 1:25, this result suggests that for 25 pregnancies with indicators like yours, 24 babies are born healthy, but only one Down syndrome.

After the screening of the blood test for the first trimester and on the basis of all the final data obtained, the laboratory can give two conclusions:

1. Positive test.
2. Negative test.

In the first case, you will have to go through a deeper examination and additional tests . In the second option, additional studies are not needed, and you can safely wait for the next planned screening that is taking place during pregnancy during the 2nd trimester.