Fetal fibronectin as a predictor of preterm birth: an overview

The objective of this study was to determine if cervicovaginal fibronectin is predictive of preterm birth. Articles involving human subjects published in English between January 1976 and December 1997 were retrieved from MEDLINE using the keywords: fibronectin, fetal fibronectin, oncofetal fibronectin, preterm, PROM, preterm birth, and preterm labor. We included studies that were prospective, enrolled women at less than 37 weeks' gestation and blinded caregivers to the fetal fibronectin test results. Of the 24 studies meeting the inclusion criteria, 15 included symptomatic women; 8 included asymptomatic women; and 1 study included both. Data were abstracted independently by two authors and a meta-analysis of results of test characteristics, using summary values, was undertaken where possible. For symptomatic women, the sensitivity for delivery within 7 to 10 days of sampling was excellent (summary value [95% confidence interval ¿CI¿]: 98% [95%, 100%]). For delivery within 14 days, the sensitivity was somewhat lower (summary value [95% CI]: 82% [74%, 90%]) and lower still for delivery within 21 days (summary value [95% CI]: 73% [67%, 80%]). For delivery less than 34 weeks the sensitivity was good, but poor for delivery less than 37 weeks (summary value [95% CI]: 87% [81%, 94%], 54% [51%, 58%] respectively). For asymptomatic women, the sensitivity of fetal fibronectin for delivery less than 34 and less than 37 weeks was poor (summary value [95% CI]: 43% [36%, 50%] and 64%[57%, 71%] respectively). The specificity of fetal fibronectin for symptomatic and asymptomatic women was over 80% for all outcomes. For symptomatic women, a negative test for fetal fibronectin should be useful at ruling out the likelihood of delivery within 7 to 10 days of sampling. For asymptomatic women, testing for fetal fibronectin is unlikely to be useful as many women at risk will be misclassified as normal.