With the full liberalization of the two-child policy, maternity checkups are becoming more and more popular. Among the various examinations, ultrasound is a very practical and irreplaceable examination. Ultrasound diagnosis can determine early pregnancy, identify whether the fetus is alive or not, accurately diagnose fetal congenital malformations and abnormal placental position through the observation of the body’s reflection of ultrasound, and is non-radioactive, non-invasive, convenient and quick. For mothers, if the pregnancy is relatively uneventful, generally speaking, a minimum of 5 ultrasounds should be performed, and each ultrasound has a corresponding gestational week requirement that cannot be missing. The first is 6~8 weeks of pregnancy: to determine the location and number of fetal sacs, to exclude ectopic pregnancy and scar pregnancy, whether the embryo is alive and to check the gestational weeks according to the fetal buds; the second is 11~13+6 weeks of pregnancy: to do the nuchal translucency layer examination, also called NT examination, the NT thickness in this gestational week is related to the risk of fetal chromosomal abnormalities, fetal malformations and the occurrence of miscarriage; the next is 20~24 weeks of pregnancy: to do the fetal system screening, i.e. Next is the 20th to 24th week of pregnancy: fetal system screening, i.e. “grand mal” ultrasonography, which can examine some of the fetal structures and exclude most of the fetal anomalies; then is the 28th to 32nd week of pregnancy: to evaluate the fetal growth and development, and further understand the development of fetal organs and structures; finally is the assessment of fetal growth and development after the full term of pregnancy, to determine the fetal position, evaluate the maturity of the placenta The last is the assessment of fetal growth and development after full-term pregnancy, determining the fetal position, evaluating the maturity of the placenta and the amount of amniotic fluid. In case of discomfort or other special conditions during pregnancy, in addition to the above 5 ultrasounds, the patient should visit the obstetrics clinic in a timely manner and the obstetrician will decide whether additional ultrasounds or other tests are needed.