The presence of a gestational sac in the uterine cavity can usually be determined by ultrasound or ultrasound at around 40 days after menopause, counting from the first day of the last menstrual bleeding. In other words, if the menstrual cycle is normal, with a monthly cycle of about 30 days, and the menstrual period is delayed for 10 days, an ultrasound or color ultrasound can be used to determine whether a pregnancy sac is developing in the uterine cavity. If there is a delay in menstruation, the examination can be delayed by a week and the chorionic gonadotropin in the blood can be checked to determine if the pregnancy is present. After the pregnancy is confirmed, an ultrasound or ultrasound is needed to determine whether the pregnancy is intrauterine or extrauterine. If the yolk sac or the fetal buds are to be observed, the test should be performed after 49 days of menopause in women with regular menstrual cycles.