Fallopian tube damage is a common cause of ectopic pregnancy. A fertilized egg can become caught in the damaged area of a tube and begin to grow there. Some ectopic pregnancies occur without any known cause.
Common causes of fallopian tube damage that may lead to an ectopic pregnancy include:
Smoking. Women who smoke or who used to smoke have higher rates of ectopic pregnancy. Smoking is thought to damage the fallopian tubes' ability to move the fertilized egg toward the uterus.