The choice of ultrasound examination after pregnancy is a strict and scientific issue, and it is not the better to check as many times as possible, nor is it possible to check several times at random, but it should be chosen scientifically according to the month of pregnancy and delivery. After pregnancy, there are three stages according to the number of days: early pregnancy, middle pregnancy and late pregnancy. 0~3 months is the early pregnancy stage, 4~6 months is the middle pregnancy stage, 7~9 months is the late pregnancy stage, and the whole pregnancy week is 40 weeks according to the week. In terms of fetal organs, there are observations related to each period. It is very important to check whether you are pregnant and to identify whether the pregnancy is intrauterine or ectopic, as it is normal to check once after the first month of pregnancy, when the signs of pregnancy first appear. However, if it is clear that the pregnancy is intrauterine, the examination should not be too long at this time, and it is enough to confirm the diagnosis of intrauterine pregnancy and the presence of fetal buds; Doppler flow function should not be used. The ultrasonographer is generally aware of this. One examination before 4 months, the general organs can be seen and checked for abnormalities, but not all of them can be checked clearly just by one time, some content is limited by the development of pregnancy. Check once before 7 months, in addition to re-checking the organs for abnormalities, mainly to determine the fetal position, and if necessary, to adjust the fetal position. Ultrasound check before 9 months, mainly to check the fetal heart rate, blood flow changes, the amount of amniotic fluid, placental maturity and position, to provide information for the delivery. In addition to the above contents of fetal organs to be observed, the fetal heart rate, amount of amniotic fluid, umbilical cord and blood flow, placenta position and maturity are routinely observed in each examination. In addition, each prenatal checkup is subject to the clinician’s decision on whether ultrasound examination is needed according to the symptoms. In general, the closer the delivery period is, the more frequent the checkups will be, so as to keep track of the changes of the fetus and escort the birth of a healthy baby.