In women who usually have regular periods, the gestational sac can be observed by ultrasound at 5-6 weeks of pregnancy to determine whether the pregnancy is intrauterine or ectopic. After intercourse between a man and a woman, if the sperm and egg unite to become a fertilized egg and successfully implant, pregnancy can be initially confirmed by urine pregnancy test and blood HCG test usually 10-15 days after intercourse. The gestational sac can be detected by more than 20 days after intercourse, when it is usually 5 weeks of pregnancy and can be seen by vaginal ultrasound, and wait for another 1 week and can be seen by abdominal ultrasound. Only when the gestational sac is seen can we confirm whether it is an intrauterine or ectopic pregnancy. In case of intrauterine pregnancy, a round or oval gestational sac can be seen in the uterine cavity. In case of ectopic pregnancy, the ectopic pregnancy mass may not be seen in the early stages of pregnancy, but the gestational sac will be seen in an extrauterine location such as the bilateral fallopian tubes or the adnexal area at about 50 days of gestation.