Subclassification of indeterminate pelvic ultrasonography: prospective evaluation of the risk of ectopic pregnancy.

Study Objective: We sought to determine the frequency of ectopic pregnancy among subclasses of indeterminate ultrasonographic examinations.

Methods: A prospective observational study was performed from January 1, 1995, to August 31, 2000, on consecutive emergency department patients in the first trimester of pregnancy with a chief complaint of abdominal pain or vaginal bleeding and who had an indeterminate transvaginal ultrasonographic examination at the time of the ED visit. Patients were excluded if lost to follow-up.