The ultrasound performance in pregnancy, firstly, in early pregnancy, the uterine body is enlarged, the endometrium is thickened, the gestational sac is visible in the uterine cavity, and the yolk sac, fetal bud and fetal heart are visible in the gestational sac. At this time, we should pay attention to the presence of gestational sacs in the adnexal area and never miss the diagnosis of ectopic pregnancy. Secondly, in middle and late pregnancy, the fetus and appendages such as amniotic fluid, placenta and umbilical cord can be seen in the uterine cavity, and the growth and development of different parts of the fetus can be observed at different times. Three important time periods to observe the fetus during pregnancy are: 1) 11th-13th gestational weeks + 6 days, this time period is used to observe the NT value i.e. the thickness of the nuchal translucency layer; 2) 20th-24th gestational weeks, used to detect fetal malformations; 3) 28th-32nd gestational weeks, used to observe the growth and development of the fetus.