Quantitative fetal fibronectin to predict preterm birth in women with previous cervical surgery

Background:Quantitative fetal fibronectin testing has demonstrated accuracy for prediction of spontaneous preterm birth in asymptomatic women with a prior history of preterm birth. Predictive accuracy in women with previous cervical surgery (a potentially different risk mechanism) is not known. 

Objective:To compare the predictive accuracy of cervicovaginal fluid quantitative fetal fibronectin and cervical length testing in asymptomatic women with previous cervical surgery to that in women with one previous preterm birth. Study Design A prospective blinded secondary analysis of a larger observational study of cervicovaginal fluid quantitative fetal fibronectin concentration in asymptomatic women measured with a Hologic 10q system (Hologic, Marlborough, MA). Prediction of spontaneous preterm birth (<30, 34 and 37 weeks) with cervicovaginal fluid quantitative fetal fibronectin concentration in primiparous women who had undergone at least one invasive cervical procedure (n=473) was compared with prediction in women who had previous spontaneous preterm birth, preterm prelabour rupture of membranes or late miscarriage (n=821). Relationship with cervical length was explored. 
Results:The rate of spontaneous preterm birth <34 weeks’ in the cervical surgery group was 3% compared with 9% in previous spontaneous preterm birth group. Receiver operating characteristic curves comparing quantitative fetal fibronectin for prediction at all 3 gestational end-points were comparable between the cervical surgery and previous spontaneous preterm birth groups; (34 weeks: area under the curve 0.78 [0.64-0.93] vs. 0.71 [0.64-0.78] p=0.39). Prediction of spontaneous preterm birth using cervical length compared with quantitative fetal fibronectin for prediction of preterm birth before 34 weeks of gestation offered similar prediction; area under the curve 0.88 [0.79-0.96] vs. 0.77 [0.62-0.92] p=0.12 in the cervical surgery group; 0.77 [0.70-0.84] vs. 0.74 [0.67-0.81] p=0.32 in the previous spontaneous preterm birth group. 
Conclusion:Prediction of spontaneous preterm birth using cervicovaginal fluid quantitative fetal fibronectin in asymptomatic women with cervical surgery is valid, and has comparative accuracy to that in women with a history of spontaneous preterm birth.