Etiology

• Fallopian tube (∼ 95% of cases)

  • Ampulla (∼ 70%)

  • Isthmus (∼ 15%)

  • Fimbriae (∼ 8%)

  • Interstitial/cornual pregnancy (∼ 2%): implantation of gestational sac in the cornua of a bicornuate or septate uterus

• Ovary (∼ 3% )

• Abdomen (∼ 1%)

• Cervix (< 1%)

Anatomic alteration of the fallopian tubes

• History of PID (e.g., salpingitis)

• Previous ectopic pregnancy

• Surgeries involving the fallopian tubes (e.g. tubectomy)

• Endometriosis

• Ruptured appendix

• Kartagener syndrome

• Exposure to diethylstilbestrol (DES) in utero

• Bicornuate uterus

Nonanatomical risk factors

• Smoking

• Advanced maternal age (> 35 years)

• Pelvic inflammatory disease

• Intrauterine device

• In vitro fertilization

• Hormone therapy