Until a few decades ago, the main emphasis was on performing examinations in the third trimester of pregnancy, but now the examination at the end of the first trimester, between 11 and 13+6 weeks of pregnancy, seems to be crucial.

At this time, fetuses with an increased risk of chromosomal aberrations can be identified. For this purpose, the assessment of nuchal translucency (HTN), the presence of a nasal bone (NB), the flow in the venous tract (DV), among others, is performed. In addition to the Medical US examination in the first trimester of pregnancy, a double test (PAPP-A and BetaHCG test) can also be performed.

The combined use of ultrasound markers and biochemical test results makes it possible to estimate the risk of the most common trisomies, namely Down, Edwards and Patau syndromes. Subsequent Medical US examinations should take place between 18 and 22 weeks of pregnancy and between 28 and 32 weeks of pregnancy.

These are aimed at a detailed assessment of the internal organs of the fetus, particularly for heart defects. In addition, with these examinations it is possible to determine the baby's growth rate and approximate fetal weight.