Serum progesterone levels as an aid in the diagnosis of ectopic pregnancy.

Progesterone levels in 29 women with ectopic pregnancies and 20 women with early intrauterine pregnancies were evaluated using a new direct radioimmunoassay that offers results within four hours. Patients with normal intrauterine pregnancies had serum progesterone levels greater than 20 ng/mL (mean = 30.9 ng/mL) while all patients with ectopic pregnancies had progesterone levels less than 15 ng/mL (mean = 5.7 ng/mL). The incorporation of the progesterone assay into the workup of a patient with suspected ectopic pregnancy can be a useful clinical adjunct to the conventional methods of evaluation.