Basic screening in the first trimester
A basic screening is conducted in the 1st trimester to reveal possible medical complications in early pregnancy and make it possible to treat them together in time. In this screening, we:
- Ascertain the exact duration of pregnancy, specify the date of birth
- Determine the size of the fetus and nuchal translucency (high nuchal translucency might be the sign of a risk of an inborn defect)
- Determine the risk of inborn defects (Down syndrome, Edwards syndrome)
The basic screening in the 1st trimester can also be called the combined test, because this test combines the results of ultrasound examination and the results of the mother's blood test, where mainly the level of PAPP A and free beta hCG fragment are monitored.
A combined test is a non-invasive examination that can successfully determine the risk of inborn defects (e.g. Downs syndrome, Edwards syndrome). This test is highly accurate and sensitive and it detects 90% of fetuses with Down syndrome, as distinct from the standard triple test where only 50-60% fetuses with Down syndrome are detected.
False positivity (incorrect positive result of a test conducted on a healthy fetus) of the combined test is considerably lower. The need to take amniotic fluid to confirm or deny a positive result is therefore lower as well. The reason we want to avoid taking and analyzing amniotic fluid is the risk of a spontaneous abortion as a result of the test.