There are normal conditions and some caused by abnormal reasons, the specific reasons and treatment methods are as follows: a. The normal situation is that the woman herself has polycystic ovary syndrome, her menstrual cycle is pushed back irregularly, and it is normal to not see the pregnancy sac on 46 days of menopause, because ovulation is late, so the time to see the pregnancy sac on ultrasound is also late. In addition, some patients have late ovulation or late implantation of fertilized eggs, which can occur in such cases. Ectopic pregnancy: the fertilized egg is in a location other than the uterus, so the gestational sac cannot be seen, and this condition requires blood tests for HCG, progesterone and imaging to confirm the diagnosis and treatment. For example, early ectopic pregnancy can be treated with mifepristone and misoprostol, and in case of ruptured ectopic pregnancy with hemorrhage, surgery is needed immediately. 2. Biochemical pregnancy: the woman’s fertilized egg does not implant, or even if it does implant, it is unstable and there is an unexpected miscarriage, so in this case the gestational sac cannot be seen. Occasional biochemical pregnancies usually do not need to be treated, while recurrent biochemical pregnancies need to be treated by finding the cause and treating the symptoms, such as taking thyroid hormone drugs or surgery.