The interval between ultrasound exams during pregnancy depends on the condition of the pregnancy, and you should follow the advice of the attending physician as to when ultrasound is needed. Ultrasound examinations during pregnancy help to detect the health of the fetus, and the time when the fetal buds can be seen during ultrasound examinations is usually around 40-50 days of gestation. In general, the obstetrics department can check once every two months before 37 weeks, and after 37 weeks until the delivery according to the change of condition, if 40 weeks is not in labor, it needs to increase once a week, if the premature rupture of membranes even need to check once every three days. In addition, the frequency of examination depends on the condition of the mother, if you feel that the fetal movement is more frequent or slow, you need to perform ultrasound and fetal heart monitoring as early as possible, and pregnant women with high blood pressure during pregnancy, gestational diabetes, fetal growth restriction, abnormal amniotic fluid and other high-risk factors should also increase the frequency of ultrasound examination. Since ultrasound has no effect on the fetus, the mother can maintain a relaxed mood and regular rest. In addition, it is necessary to hold urine before the ultrasound examination in early pregnancy. Pregnant women should wear wide and easy-to-removal clothes and shoes during the examination and actively cooperate with the doctor.