Diagnostic value of cervical fetal fibronectin in detecting extrauterine pregnancy

Abstract Objective: To determine whether fetal fibronectin (FFN) might serve as a marker to distinguish intrauterine versus extrauterine pregnancy. Design: Prospective cohort study. Setting: Academic research center. Patient(s): Cervicovaginal FFN samples were obtained from 46 women who were at high risk for or presented with signs and/or symptoms of extrauterine pregnancy. Intervention(s): Samples of blood were analyzed for FFN with use of an enzyme-linked immunoabsorbent assay (ELISA). Main Outcome Measure(s): Fetal fibronectin level. Result(s): The rate of extrauterine pregnancy in our study was 26.1%, with 12 extrauterine and 34 intrauterine pregnancies identified by ultrasonography or at time of surgery. Seventeen samples had FFN levels of >50 ng/mL and were considered positive (range, 0–1,000 ng/mL). Positive FFN levels were observed in 41.7% (5 of 12) of women with extrauterine pregnancies versus 35.3%) (12 of 34) of women with intrauterine pregnancies. The sensitivity, specificity, and positive and negative predictive values for extrauterine pregnancy were 41.7%, 64.7%, 29.4%, and 75.9%, respectively. Conclusion(s): The use of FFN does not appear to alter significantly the likelihood of identifying extrauterine pregnancy over current laboratory or ultrasonographic methods.