The decision will depend on the week of pregnancy and the underlying status of the pregnant woman. Ultrasound examinations in different weeks of pregnancy have different purposes. Ultrasound examinations in early pregnancy are mainly performed to determine whether the pregnancy is intrauterine or extrauterine, and if the first ultrasound does not show an obvious gestational sac, ultrasound examinations are still needed within a week. Ultrasound in middle pregnancy is to check if there is any obvious structural malformation of the fetus, and if there is no special case, ultrasound is usually needed once a month. Ultrasound in late pregnancy is mainly to check the development of the fetus and to assess the weight of the fetus when it enters the due date to guide the choice of delivery method. If any abnormalities are found during pregnancy, regular follow-up visits and more frequent examinations are needed. Pregnant women are advised to have regular maternity checkups and follow the advice of their professional doctors.