Mifepristone and Misoprostol for Undesired Pregnancy of Unknown Location.

Objective: To compare immediate initiation with delayed initiation of medication abortion among patients with an undesired pregnancy of unknown location.

Methods: This retrospective cohort study used electronic medical record data from the Planned Parenthood League of Massachusetts (2014-2019) for patients who requested medication abortion with a last menstrual period (LMP) of 42 days or less and pregnancy of unknown location (no gestational sac) on initial ultrasonogram. Clinicians could initiate medication abortion with mifepristone followed by misoprostol while simultaneously excluding ectopic pregnancy with serial serum human chorionic gonadotropin (hCG) testing (same-day-start group) or establish a diagnosis with serial hCG tests and repeat ultrasonogram before initiating treatment (delay-for-diagnosis group).