There are 2 techniques,�direct method�and�indirect method, used to investigate renal arterial supply. Both ideally are used in conjuction with each other, however, in circumstances where the renal artery is not seen in its entirety then the indirect approach alone can give an indication of vascular disease.
Early in pregnancy it is often done to make sure the foetus is inside the uterus and to check the foetal heart rate, later on in pregnancy it is often done to check - the growth and position of the foetus, position of the placenta and the amount of the amniotic fluid.
Ultrasound Limited Obstetrical (also known as level 1 ultrasound) is performed to answer a specific, clinical question, when there is no time or need to do the more extensive basic sonogram. The Limited ultrasound often takes only a few minutes and can be done anytime in pregnancy.