Patients often ask why ectopic pregnancy occurs when IVF is not done by placing the embryo in the uterine cavity. The incidence of ectopic pregnancy (EP) in in vitro fertilization-embryo transfer (IVF-ET) has been reported in the literature to range from 2.1% to 8.6%. The incidence of ectopic pregnancy after IVF-ET is increased compared with that of natural pregnancies, which is associated with tubal pathology, a history of ectopic pregnancy, and difficulty in transferring the embryos. Some experimental studies have found that embryos transferred into the uterine cavity sometimes flow into the fallopian tube with the culture fluid, when the fallopian tube is functioning normally, it can transport the embryo in back to the uterine cavity, but when the fallopian tube and pelvic pathology, the normal peristaltic movement of the fallopian tube disappeared, so it can’t transport the embryo back to the uterine cavity, and then ectopic pregnancy will occur. In addition when doing IVF, poor quality embryos, transferring a large number of embryos, or suffering from endometriosis can lead to a higher incidence of ectopic pregnancy.