Role of transmigration and abnormal embryogenesis in ectopic pregnancy.

Transmigration of ovum and/or sperm may occur, as deduced by the presence of EP in the fallopian tube contralateral to the corpus luteum. The frequency of occurrence of transmigration is relatively low, and, in many cases, other routes of ovum and sperm transport (i.e., intrauterine migration, tubal recanalization, fistula formation) may lead to the ectopic implantation site. In our view, the percentage of abnormal embryos associated with EP is no different from those associated with spontaneous abortions of intrauterine origin. Embryos from spontaneous abortions-of either intrauterine or extrauterine origin-seem to have more abnormalities than embryos from induced abortions. Other etiologic factors such as tubal disease, strictures of the fallopian tube, or endocrinopathies seem to contribute more significantly to the incidence of EP than does abnormal embryogenesis.