Single progesterone assay for early recognition of abnormal pregnancy.

Serum progesterone and human chorionic gonadotrophin (HCG) were analysed using a time-resolved fluoroimmunoassay in an unselected group made up of 158 women with clinical suspicions of abnormal early gestation. Only cases in which endovaginal sonography had failed to localize the pregnancy were included. A single HCG determination had no diagnostic value. On the other hand, a critical progesterone level of 30 nM was determined below which no viable intrauterine pregnancies were found. Eighty-eight per cent of the ectopic pregnancies (n = 97) and 83% of the spontaneous abortions had progesterone levels below this limit. The discriminatory efficacy of one single progesterone determination was independent of the actual HCG level and serial determinations of progesterone did not increase the discriminatory power.