PRENATAL TESTS – 1ST TRIMESTER
The first trimester ultrasound scan, popularly referred to as GENETIC TEST IN THE 1ST TRIMESTER, is performed between weeks 11+0-13+6 of pregnancy. Since many women do not menstruate on a regular basis or their menstrual cycle length is different from 28 days*, the most important thing is the actual size of the baby – or more precisely, its crown-rump length (CRL) – which is the distance from the top of the head to the buttocks, that must be between 45 and 84 mm, whereas other measurements are interpreted on this basis. *This information should also be taken into account when registering for the test.
At this stage of foetus development, we initially assess the anatomical structure: the structure and dimensions of the head (BPD), chest and belly, upper and lower limbs (FL), the structure and flows in the heart, venous duct and umbilical cord, the presence of the stomach and bladder, the position of the chorion. We also assess the so-called genetic markers included in the risk calculation software: NB (nasal bone), NT (nuchal translucency), TV (tricuspid valve flow in the heart), DV (ductus venosus blood flow), FHR (fetal heart rate). The markers or defects found at this stage significantly affect the risk of giving birth to a child with chromosomal aberration.
At this stage, it is possible to significantly increase the sensitivity of screening tests to a level that can detect up to 95% of foetuses with frequent chromosomal aberrations. For this purpose, we will also take your blood for a biochemical test to assess the concentrations of certain substances that change in a specific way during pregnancy and their abnormal levels may increase the risk of diseases. As in the case of ultrasound markers, this is not a diagnosis of any diseases, but only determination of their risk.
DOUBLE TEST (fβhCG + PAPP-A) – a biochemical test performed between weeks 10 – 13+6 of pregnancy, usually performed in parallel with the ultrasound scan, sometimes even earlier.
PLGF – assessment of the level of this biochemical marker, which can be performed simultaneously with the double test from the same blood sample, enabling a more precise calculation of the risk of preeclampsia development.
The calculation of individual risk based on medical data, interview and marker assessment is currently the recommended method for detecting patients at risk of preeclampsia development during pregnancy.
NOTICE: If the patient comes to us earlier and the size of the foetus does not meet the criteria for measuring ultrasound markers (CRL < 45 mm), but the size of the foetus corresponds to the size of week 10 of pregnancy, we will only take a blood sample and arrange for the foetus ultrasound assessment in about 2 weeks.
However, if the patient comes for the examination later, i.e. the foetus CRL is greater than 84 mm, it is also possible to perform ultrasound screening and biochemical examination.
Pregnancy week 14-18
The ultrasound scan performed during this period of pregnancy, similarly as in the first trimester, assesses the correctness of the child’s development and enables the assessment of several genetic markers.
At this stage, neck translucency (NT) can no longer be assessed as the sensitivity and specificity of this marker decreases significantly after the first trimester of pregnancy. During this period, examination of the child is usually the most difficult and, due to lower specificity of the markers, is less accurate. The examination at this time is also technically difficult, mainly due to the position of the child.
There is also a biochemical test that can be performed at this stage.
TRIPLE TEST (AFP,hCG,uE3) – a biochemical test from the mother’s blood performed between week 14 – 18 of pregnancy in parallel with the ultrasound scan. Sensitivity of the triple test is significantly lower than the double test when it comes to detecting genetic syndromes. Nevertheless, this test enables the early detection of open spinal defects in the foetus. Due to lower sensitivity of this test, there is a tendency to give up this test in favour of testing free DNA from the mother’s blood.
With a correct first trimester screening result, this stage is usually omitted.
At every stage of pregnancy, starting from the week 10, it is possible to perform additional tests – FETAL DNA – increasing the sensitivity of detecting the most common chromosomal aberrations in different percentages.