Blind vaginal fetal fibronectin swab for prediction of preterm birth

To assess the accuracy of blind vaginal swab in diagnosis of preterm labor (PTL) and prediction of subsequent occurrence of preterm birth (PTB).

Eligible women who presented at 24-34 weeks of gestation with threatened PTL had their cervicovaginal secretions sequentially sampled for fetal fibronectin (fFN) using two types of swabbing techniques. The first swab was a blind vaginal swab collected without the aid of speculum, while the second one was a routine cervicovaginal swab. All participants were followed up until delivery.

fFN in both swabs was significantly higher in women who delivered before term compared with women who delivered at term. On regression analysis, r(2) = 0.735 and 0.785 for blind vaginal and cervicovaginal swabs respectively, while on receiver operating characteristic analysis the area under curve was 0.965 and 0.977, respectively, without a statistically significant difference. Using an fFN cut-off of ≥0.05 μg/dL, the sensitivity, specificity, positive predictive value and negative predictive value of blind vaginal swab to predict PTB were 53.9%, 91.9%, 70.0% and 85.0%, respectively; while those for cervicovaginal swab were 58.3%, 94.7%, 77.8% and 87.8%, respectively.

In women presenting at 24-34 weeks of gestation with threatened PTL, blind vaginal fFN swab is as effective as cervicovaginal swab to predict PTB, but it is easier to perform and does not require doctor supervision.