Normally, pregnant women need to have an ultrasound about 4 times throughout their pregnancy, up to a maximum of 6 times. However, the number of ultrasound sessions varies from woman to woman after pregnancy due to the specific circumstances that arise. If a woman does not have abdominal pain, vaginal bleeding and other symptoms of preterm miscarriage or preterm labor, it is most appropriate to have 5 ultrasounds during pregnancy, mainly at about 45 to 50 days of pregnancy, to confirm intrauterine pregnancy and to see the fetal heartbeat and fetal buds; in the third trimester, when the card is established at about 20 weeks, to see the nuchal transparency and nasal bones of the fetus and to deduce the best time for Down’s syndrome screening; in the fourth trimester, when the card is established at about 20 weeks, to have an ultrasound. In the fourth month of pregnancy, an ultrasound is needed for Down’s syndrome screening; at 24 weeks of pregnancy, a 4D ultrasound is needed for a major abnormality test; and finally, between 35 and 39 weeks of pregnancy, one or two ultrasounds may be needed near the due date. If there is vaginal bleeding and other signs of preterm miscarriage during pregnancy, it is often necessary to increase the number of ultrasound examinations. For cases such as poor fetal growth and low amniotic fluid in late pregnancy, it is also necessary to increase the number of examinations to see the growth and development of the fetus and to see the growth of amniotic fluid. Therefore, it is generally about 4 to 6 times, but the number of times may vary in different cases. There is no specific limit to the number of ultrasounds that can be performed during pregnancy, which can only be determined by the specific circumstances of the pregnant woman.