The HCG value of pregnant women is close to 2000mIU/mL at 4-6 weeks of gestation, and the gestational sac can be seen in the uterine cavity by vaginal ultrasound at 35 days of menopause in women with regular menstruation, which is about 5 weeks of pregnancy, and the gestational sac can be seen in the uterine cavity by abdominal ultrasound at 6 weeks of gestation, so the gestational sac may be seen at 2000mIU/mL of HCG. Clinically, ultrasound examination is generally recommended at 6 weeks of gestation. At 5-6 weeks of gestation, the fetus starts to develop slowly and the amniotic cavity expands accordingly, at which time the examination can not only see the gestational sac, fetal bud and fetal heartbeat, but also diagnose the presence of ectopic pregnancy or other pregnancy diseases. At 4-5 weeks of gestation, the fertilized egg is not long in the uterine cavity and the gestational sac cannot be seen on the ultrasound. In this early stage of pregnancy, pregnant women should pay attention to their diet, avoid strenuous exercise, stay away from harmful substances, maintain emotional stability, have regular checkups, and seek medical consultation when they are unwell.