Cause

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 develop without any known cause. See a picture of locations where an ectopic pregnancy can develop.

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. The more you smoke, the higher your risk.¹ Smoking is thought to damage the fallopian tubes' ability to move the fertilized egg toward the uterus.
• Pelvic inflammatory disease (PID), such as from a chlamydia or gonorrhea infection. PID can create scar tissue in the fallopian tubes.
• Fallopian tube surgery, often used to reverse a tubal ligation or to repair a scarred or blocked tube.
• A previous ectopic pregnancy in a fallopian tube.

Although pregnancy is rare after a tubal ligation or with an intrauterine device (IUD), those pregnancies that do develop have an increased chance of being ectopic.²