The preterm prediction study: Fetal fibronectin testing and spontaneous preterm birth*

Objective To evaluate the presence of fetal fibronectin in the cervix and vagina as a screening test for spontaneous pretenn birth. Methods Two thousand nine hundred twenty-nine women at ten centers were routinely screened every 2 weeks from 22–24 to 30 weeks for cervical and vaginal fetal fibronectin. A positive test was defined as a value equal to or greater than 50 ng/mL. The relation between a positive test at four gestational ages and spontaneous preterm birth at various intervals after the test was determined. Results In each testing period, 3–4% of the fetal fibronectin tests were positive. The correlation between cervical and vaginal fetal fibronectin at the same visit was always approximately 0.7 ( P P Conclusion A positive cervical or vaginal fetal fibronectin test at 22–24 weeks predicted more than half of the spontaneous preterm births at less than 28 weeks (sensitivity 0.63). As the definition of spontaneous preterm birth was extended to include later gestational ages or when the fetal fibronectin test was performed later in pregnancy, the level of association between a positive fetal fibronectin test and spontaneous preterm birth, while remaining highly significant, tended to decrease. Although fetal fibronectin is an excellent test for predicting spontaneous preterm birth, we present no evidence that the use of this test will result in a reduction in spontaneous preterm birth.