Background: Women are seeking abortion at increasingly earlier gestations which increases the likelihood that providers will have difficulty visualizing the pregnancy on ultrasound, the current standard of care in most abortion clinics in the US. Women with no gestational sac visualized on ultrasound have a pregnancy of unknown location (PUL). The most serious risk of initiating medication abortion with a PUL is a missed diagnosis of ectopic pregnancy. Several national organizations enable provision of medication abortion in the setting of PUL, when the patient is low-risk for ectopic and when combined with close follow up to exclude ectopic. In deciding whether to initiate the medication abortion immediately and simultaneously start serial hcg testing to exclude ectopic (same-day start) versus delaying the abortion to first confirm intrauterine pregnancy (delay-for-diagnosis), clinicians must assess both the individual’s underlying risk of ectopic, the likelihood of adherence to recommended follow-up and the most efficient way to rule-out ectopic. Methods: This retrospective cohort study will assess the relative safety and efficacy of offering medication abortion as “same-day-start” compared to “delay-for-diagnosis” for women presenting with low-risk PUL.

Proposed analysis: We will measure which management strategy is associated with the shortest time to rule-out, or diagnose, an ectopic and whether loss-to-follow-up without a definitive diagnosis (a liability) differs for same-day-start versus delay-for-diagnosis patients. We will also compare adverse events, medication abortion efficacy, time to complete abortion and resource utilization with each management strategy. If ectopic is excluded more rapidly and efficacy and loss-to-follow-up rates are comparable, there is no reason to delay.