A single visit protocol based on serum progesterone measurements appears to be a safe and effective approach for triaging and managing women with pregnancy of unknown location (PUL). A total of 6,201 women with suspected early pregnancy complications attended King's College Hospital, London over the 15-month study period. There were 676 (10.9%) with PUL, defined as a positive pregnancy test but with no evidence of a gestation sac in utero or ectopic on ultrasound scanning. Of these 252 were found to have a progesterone level <10 nmol/L. All but one of these women were treated as outpatients and were not invited for further investigation.