Many pregnant women keep asking to do ultrasound, early pregnancy, mid-pregnancy and even late pregnancy, but in fact, the significance of ultrasound for different periods of time is not known, here I briefly introduce: (1) early pregnancy: generally there are no special circumstances, such as abdominal pain, vaginal bleeding, or ectopic pregnancy high-risk factors do not recommend ultrasound, if there are indications of the recommendation of the line of vaginal ultrasound, because at this time, vaginal ultrasound is the most accurate, and the study has not yet found that early Vaginal ultrasound in early pregnancy has not been found to be teratogenic. (2) NT at 12 weeks: Generally speaking, ultrasound at this period can only detect some serious fetal abnormalities, such as total forebrain, etc. We mainly focus on the thickness of nuchal translucency, which is closely related to chromosomal abnormalities in the fetus. (3) Ultrasound around 22 weeks: this is the best time to detect fetal abnormalities, so we suggest that all pregnant women should go to qualified hospitals for ultrasound screening of fetal abnormalities. (4) Ultrasound at around 30 weeks: Due to the size of the fetus, ultrasound screening for abnormalities cannot be performed at this time, but it is of special significance for some brain abnormalities such as widening of the lateral ventricles that become more obvious in the late stages of pregnancy, and so on. Therefore, at this time, the main purpose is to perform biometric measurements on the fetus, amniotic fluid volume measurements, and umbilical vascular Doppler measurements, and so on. (5) Ultrasound at 36 weeks: At this time, the fetus is obviously enlarged, and the value of screening for anomalies is reduced, so the main purpose is to clarify the position of the fetus, fetal biometrics, amniotic fluid volume measurement, umbilical vascular Doppler measurements, and so on.