There is no strict time requirement or limitation for ultrasound examination, and the decision is mainly based on your own situation and the purpose of the examination. 1. People without special conditions: Healthy people without special conditions can generally do ultrasound once every 1-2 years to screen for thyroid, breast, liver, cardiovascular and other diseases. 2. People with special diseases: If you suffer from special diseases, you need to determine the time interval of ultrasound according to the specific conditions, such as malignant tumors, generally every three months to do an ultrasound to observe the tumor, and benign tumors, generally every six months to review the ultrasound. 3. Pregnant women: Pregnant women need regular pregnancy checkups, generally at 6-7 weeks of pregnancy need to do ultrasound to check whether the fetus is alive, to rule out ectopic pregnancy; 11-13 weeks of pregnancy ultrasound can be detected NT value, in order to assess the risk of chromosomal abnormalities in the fetus; 22-26 weeks of pregnancy need to carry out ultrasound screening, to check the fetus for anomalies. After this, ultrasound is also performed around 32, 37 and 40 weeks of pregnancy. Additional ultrasound is also required if the pregnant woman has abnormal vaginal bleeding or abdominal pain. Ultrasound is highly safe, causes little damage to the human body, and is of high value in the qualitative and localized diagnosis of diseases, so it is more widely used in clinical practice. Different people should undergo ultrasound examination according to their own conditions and under the advice of their doctors.