If a gestational sac cannot be seen in the vaginal examination on 40 days of pregnancy, there may be several cases: 1. The patient’s menstrual cycle is irregular or prolonged, or the menstrual cycle may be regular, but the ovulation time of each cycle is irregular, then the time of conception has reached 40 days according to the last menstrual period, but the actual time of conception has not reached 40 days. At this time, the gestational sac cannot be seen in the uterus on ultrasound, so the examination can be postponed for a week, or the chorionic gonadotropin measurement can be performed in time, and if the hormone doubling situation meets the pregnancy criteria, the gestational sac can be waited for; 2. Ectopic pregnancy, the most common ectopic pregnancy is tubal pregnancy, and the gestational sac cannot be seen in the uterus, so a detailed and extensive scan should be done in the pelvis to look for suspected ectopic pregnancy masses. If no gestational sac is temporarily seen in the uterus and no suspicious mass is seen in the ectopic scan, then timely review and close observation can be done according to the patient’s clinical manifestations and HCG status; 3. Embryonic dysplasia leading to biochemical pregnancy, or early abortion cannot be excluded. However, the diagnosis of the above disease also requires timely HCG chorionic gonadotropin measurement, observation of doubling, and further clarification of the diagnosis based on doubling and clinical manifestations.