It is not necessary to have an empty stomach for an ultrasound to examine the fetus in pregnancy. In the early stages of pregnancy, that is, less than three months of pregnancy, it is necessary to fill the bladder during the ultrasound to examine the fetus, because at this time the uterus is not very obviously enlarged and it is also disturbed by the surrounding intestinal gas, so it is necessary to hold urine to fill the bladder and push away the surrounding intestinal gas so that the image can be displayed more clearly. In the middle and late stages of pregnancy, it is not necessary to hold urine to check the fetus, because at this time the uterus is obviously enlarged and the image of the fetus in the uterus is displayed very clearly, and the pregnant woman can drink and eat without being affected. However, when a pregnant woman wants to examine her digestive system, that is, the liver, gallbladder, pancreas and spleen, she needs to fast for at least 4-6 hours, because eating will affect the observation of the gallbladder, liver and pancreas, so she should fast at this time.