Many pregnant women ask during ultrasound exams, “Does ultrasound have any effect on the baby? How many times should I do it during the whole pregnancy? How about doing so many times?” A. Prenatal ultrasound is safe when used correctly Ultrasound, as a non-invasive prenatal diagnostic technique, is widely used in clinical practice for its simplicity, rapid diagnosis and repeatability. At present, it has tended to be popularized, early and repeated. When a pregnant woman goes to the hospital for a maternity checkup, ultrasound is essential. Ultrasound examination can determine the gestational week, diagnose fetal structural malformations, and monitor the intrauterine development of the fetus. With the widespread use of ultrasound, there is also concern about the safety of ultrasound examinations. The mechanisms of action of ultrasound in human tissues are divided into two categories: thermal and mechanical effects. Thermal and mechanical indices are incorporated into ultrasound safety standards, and there are corresponding safety indicators for the acoustic output of ultrasound examinations. The corresponding parameters set by the color Doppler ultrasound diagnostic instruments now in use are strictly controlled within the safety limits. Therefore, ultrasound examinations conducted in accordance with the specifications are safe, and at present, there are no reports of harmful biological effects caused by ultrasound examinations at home and abroad. The number of ultrasound examinations needed during pregnancy (excluding special cases: multiple pregnancy, placenta praevia, intrauterine distress, etc.) In view of the current situation of ultrasound examination in our department, the ultrasound examinations needed throughout pregnancy are as follows: 1. 7 weeks of pregnancy (to determine whether the pregnancy is intrauterine and whether there is fetal heart) 2. 11-13+6 weeks of pregnancy (to determine the gestational week and measure NT value) 3. 22-24 weeks of pregnancy (systematic ultrasound examination) The fetus will be screened for structural malformations. 4.32 weeks of pregnancy (to monitor fetal growth and development and screen for late onset fetal malformations) 5.37-38 weeks of pregnancy (to assess the size of the fetus) 6.The corresponding ultrasound examination will be performed before the delivery according to the doctor’s need.