1.When the qualitative or quantitative test of HCG is positive or weakly positive. 2.When there is vaginal bleeding, the amount is often less than the menstrual amount (dripping and irregular), the possibility of ectopic pregnancy should be highly pregnant. If HCG (+), no vaginal bleeding, and no intrauterine gestational sac is seen, special attention should be paid to exclude interstitial pregnancy (transverse uterine section is important). 3, Intrauterine pregnancy is more likely when the endometrial thickness is ≥15 mm, but care should be taken to exclude interstitial/isthmic pregnancy. 4. In case of small cystic dark areas or masses in the uterine cavity, early pregnancy or intrauterine pseudogestational sac should be identified based on color Doppler flow (presence of peritrophoblastic blood flow)? Intrauterine incomplete abortion or a blood clot? 5. Can the adnexal mass be separated from the ovaries? If it can be separated, it will increase the confidence in the diagnosis of ectopic pregnancy. 6. Is there any peritrophoblastic blood flow within the adnexal mass? If there is, it will increase the confidence of diagnosing ectopic pregnancy. 7. The peritrophoblastic flow is characterized by high velocity low resistance (>60cm/s, RI<0.4); high velocity venous flow (>30cm/s). 8.If high velocity low resistance and high velocity venous flow spectrum are present at the suspected mass, or if high resistance flow spectrum (RI≥1.0) is present, it can increase the confidence of diagnosing ectopic pregnancy. 9. Criteria for confirmation of early pregnancy: yolk sac and/or germ and heart tube pulsation are seen in the gestational sac.