Fetal fibronectin testing not always so accurate

The specificity and sensitivity of fetal fibronectin (fFN) testing are significantly lower for predicting delivery at less than 30 weeks' gestation in asymptomatic women with cervical cerclage than they are in women without cerclage, according to a retrospective, observational study from London.

The study included 910 asymptomatic women at high risk for preterm birth who were referred to specialist antenatal clinics between the years 1997 and 2007 and who underwent fFN testing between 23 and 27 weeks' gestation.

Researchers calculated a specificity of 77% in women with cerclage in situ versus 90% in women without (P≤.00001) and a sensitivity of 60% in women who received the procedure versus 78.6% in women who did not (P>.4). The negative predictive value (NPV) of the fFN test, however, was greater than 98% in both groups.

Duhig KE, Chandiramani M, Seed PT, et al. Fetal fibronectin as a predictor of spontaneous preterm labour in asymptomatic women with a cervical cerclage. BJOG. 2009;116:799-803.