A gestational sac in the left uterine horn is not always correct. A pregnancy in the uterine horn is when the gestational sac is implanted in the uterine horn area, whereas the normal site of pregnancy should be in the uterine cavity of the uterine uterus, therefore, pregnancy in the uterine horn area also belongs to a kind of ectopic pregnancy, which is one type of ectopic pregnancy that we are talking about. Ultrasound is an effective test to see where the gestational sac is implanted. If the gestational sac is implanted in the uterine cavity, it is only slightly shifted towards the uterine corner, and as the embryo grows, it will move towards the uterine cavity until it occupies the entire uterine cavity. However, if the gestational sac is implanted in one corner of the uterus, or even has grown so large that the muscle layer in the corner of the uterus has become thin and hardly moves towards the uterine cavity, then it is an ectopic pregnancy.