The effect of blood staining on cervicovaginal quantitative fetal fibronectin concentration and prediction of spontaneous preterm birth

Blood stained swabs have elevated qfFN concentrations but may still have predictive value, and clinical utility. Very low fFN values (<10 ng/ml) are especially reassuring and indicate lower risk of delivery than non-blood stained swabs. The higher false positive rate must be noted and explained to the patient.