Usually pregnant women need to have two ultrasounds after 30 weeks of fetal life, one at 30-32 weeks of pregnancy and the other at 38-40 weeks of pregnancy. If there are high-risk factors, the number of ultrasounds can be increased as appropriate. Ultrasound examinations are performed at 30-32 weeks of pregnancy to check the fetal growth and development, listen to the fetal heartbeat, to further rank the abnormalities and to check the position of the placenta and the condition of the fetal previa. If the examination reveals that placenta praevia may exist, medication should be applied to suppress contractions, prevent infection and correct anemia, and if the fetus is not developing well, timely detection and intervention can be made, and if necessary, the pregnancy can be terminated to avoid more damage to the pregnant woman. The purpose of ultrasound examination at 38-40 weeks of pregnancy is to check the size of the fetus, fetal position, placental maturity and the condition of the amniotic fluid in preparation for delivery. If the amniotic fluid is too low, appropriate rehydration can be done to improve the function of the placenta; if the amniotic fluid is too high, maternal diseases such as diabetes and hypertension should be taken into consideration and targeted interventions should be carried out after the examination. The number of examinations varies from one pregnant woman to another. If a pregnant woman has abdominal pain, vaginal bleeding, frequent or reduced fetal movement, abnormal fetal development or unclear fetal position during pregnancy, the number of examinations should be increased appropriately according to the specific situation. In addition to the ultrasound examination, pregnant women need to pay attention to the fetal heartbeat monitoring at 30 weeks to observe the fetal development and growth to ensure the normal growth and development of the fetus.