Failed tubal sterilization as an etiologic factor in ectopic tubal pregnancy.

An indirect statistical method was used to demonstrate that failed tubal sterilization must be considered as a significant etiologic factor in tubal ectopic pregnancy. Since the exact incidence of poststerilization pregnancies was unknown in our population, a "theoretical" incidence of a 0.71% failure rate was used as the most realistic estimate on the basis of published reports of failed tubal sterilizations. From this figure the "expected" number of poststerilization conceptions, both total and tubal, was computed. The observed incidence of poststerilization ectopic tubal pregnancy was found to be 20 times the "expected" incidence in our population.