A Doppler ultrasound is a radiological investigation which uses reflected sound waves to see how blood flows through a blood vessel. It helps clinicians evaluate blood flow through major arteries and veins, such as those of the arms, legs, and neck. During pregnancy, a Doppler ultrasound can be used to evaluate blood flow in an unborn baby to check the health of the fetus. It is a non invasive technique in which there is no risk of radiation exposure. It is totally safe during pregnancy. Preparation for Colour Doppler:Avoid nicotine products like cigarette and tobacco for about 2-4 hours prior to the Doppler test procedure. Nicotine causes the blood vessels to constrict and this may be mistaken for a pathological constriction.The patient is asked to remove any jewellery or metal accessories as it may interfere with the examination results.For abdominal scan, the patient would be asked to eat low-fiber diet for a day before the test, to minimize gas in the gut.