Tubal injury is the most common cause of ectopic pregnancy. An ectopic pregnancy occurs when a fertilized egg is stopped at the site of injury and begins to grow and develop, but fails to enter the uterus. There are other ectopic pregnancies for which no clear cause can be found. They are as follows: 1. Tubal infection: it is the most common cause of tubal pregnancy and is due to inflammation leading to tubal blockage. If the fallopian tube is completely inaccessible, it will cause infertility. Passage but not smooth can cause ectopic pregnancy; 2. Abnormal function of the fallopian tube caused by tubal surgery can cause ectopic pregnancy; 3. Tubal dysplasia or functional abnormalities: the fallopian tube has a certain length, which is normally about 10-14 centimeters. If the fallopian tube is too long, the fertilized egg will bed in the process of tubal wandering and not reach the uterine cavity, which will also form ectopic pregnancy; 4, the opposite side of the fertilized egg will bed in the fallopian tube during the process of bed wandering because of longer time; 5, more assisted reproductive technology in recent years can also cause ectopic pregnancy; 6, endometriosis or tumor compression mainly causes tubal deformation and functional abnormalities, causing ectopic pregnancy.