Fetal fibronectin as a marker to discriminate between ectopic and intrauterine pregnancies.

Abstract

Our purpose was to determine the accuracy of fetal fibronectin values for diagnosing ectopic pregnancies. We obtained vaginal swabs from women with pregnancies of < or = 12 weeks' gestation to perform enzyme-linked immunosorbent assays for fetal fibronectin. Fetal fibronectin values were compared among groups categorized on the basis of clinical and laboratory criteria into (1) ectopic pregnancies, (2) threatened abortions, (3) incomplete/complete abortions, and (4) uncomplicated intrauterine pregnancies. Mean fetal fibronectin values ranged from 0.08 microg/mL in women with ectopic pregnancies to 0.33 microg/mL in women with threatened abortions. Comparing these two diagnostic categories, a negative fetal fibronectin test (at a cutoff level of 0.300 microg/mL) predicted ectopic pregnancy with a sensitivity of 94%, specificity of 28%, positive predictive value of 62%, and negative predictive value of 78%. Although fetal fibronectin is low in women with ectopic pregnancies, a negative test is not sufficiently sensitive and specific to be used clinically for the diagnosis of ectopic pregnancy.