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.

In all, 212 of the 227 women (93%) with PUL who completed telephone follow-up had no problems. Fifteen women had problems mainly with bleeding and/or pain and attended hospital for further visits. Of these, five had ectopic gestation, two of which required laparoscopic surgery.

The others resolved spontaneously. Another woman was laparoscoped; no ectopic was found, and another had an evacuation of the uterus.

These four operative intervention cases constituted just 1.8% of the 'PUL with low progesterone level' group. The positive predictive value of serum progesterone at a cut off of <10 nmol/L for diagnosing a spontaneously resolving pregnancy was 98.2% (95% CI: 96.8-99.7%).

This prospective study did not address costs; progesterone assay obviously has a financial implication. However, against this one must weigh the significant reduction in repeat hCG assays, ultrasound scans and clinic attendances.

Dr Chris Barclay