RESUMEN
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.