First, there is the first ultrasound, which is worth going to at about 6 weeks, because then the embryo will most likely have a heartbeat, so the doctor can diagnose a live pregnancy. This is even a vaginal ultrasound. After that, at week 12, there is a larger genetic ultrasound, at which time gross developmental abnormalities are screened out. Your doctor will sort it out, it can be vaginal or even ultrasound. The next examination at week 18 is also a form of genetic ultrasound, at which point further developmental abnormalities are ruled out. After this, between weeks 28 and 32, doctors date the next examination, in which they look at the size of the fetus, mainly to deduce the expected date of delivery, but also to look at the degree of maturity of the placenta. The last test is at week 38, where they are already looking at the amount of amniotic fluid and whether the pregnancy can continue, or whether there are already risk factors that indicate that it is safer to terminate the pregnancy, ie to start giving birth. from the perspective of both the child and the mother. An over-mature placenta could be such a source of danger for example.