For women who have regular menstrual cycles, once every 28-30 days, 35 days of menopause, which is usually about 5 weeks. The gestational sac can be seen in the uterine cavity by vaginal ultrasound. Women with longer menstrual cycles tend to ovulate and conceive relatively late and may see the gestational sac a little later. It is normal for the location of the gestational sac to be at the fundus, anterior wall, posterior wall, upper part, or middle of the uterus, and to be round or oval in shape and relatively clear. If the gestational sac is irregular, blurred and located in the lower part of the uterus, and if the pregnancy is accompanied by abdominal pain or vaginal bleeding, miscarriage may occur. The fetal buds and heart tube pulsations are usually visible at 6 weeks of pregnancy, and the colorful blood flow in the fetal heart area can be seen by color Doppler ultrasound, and the fetal age can be estimated based on the size of the fetal buds in the gestational sac, and the heart tube pulsations can also be used to confirm that the embryo is alive. If the gestational sac cannot be seen on the 50th day of pregnancy, it is necessary to determine whether an ectopic pregnancy has occurred. If the gestational sac is smaller than the actual number of days of menopause due to delayed menstruation, late ovulation and late conception due to emotional stress, etc., and after 1 week of dynamic examination, the chorionic gonadotropin and progesterone values increase, the gestational sac continues to grow, and the germ and fetal heart appear, it means that the small gestational sac is due to physiological reasons and is normal and the pregnancy can continue.