Tubal ectopic pregnancies occur when transport in uterine tube is blocked. Obstruction can be result of tubal inflammation.
https://en.wikipedia.org/wiki/Ectopic_pregnancy#/media/File:Ectopic_pregnancy_on_laparoscopy.png
Reference:
Sunday-Adeoye I, et al. (2011) "A 30-year review of advanced abdominal pregnancy at the Mater Misericordiae Hospital, Afikpo, southeastern Nigeria (1976-2006)." Arch Gynecol Obstet. 283(1):19-24.