Normally, an egg is fertilized in the fallopian tube and becomes implanted in the uterus. However, if the tube is narrowed or blocked, the egg may move slowly or become stuck in the fallopian tube. The fertilized egg may never reach the uterus, resulting in an ectopic (mislocated) pregnancy.

An ectopic pregnancy may be located in many different places, including a fallopian tube, an ovary, the cervix, and the abdomen.