The purpose of this study was to estimate the effect of sonographic cervical length (CL) and fetal fibronectin (FFN) on length of evaluation and outcomes in women with preterm labor (PTL). Women with threatened PTL were randomized to either a knowledge group (results of CL and FFN available and used according to study protocol), or a standard group (blinded to CL and FFN). Primary outcome was length of evaluation in triage. One hundred women were randomized. There was no significant difference between groups in length of evaluation, but in women with CL > or = 30 mm, the mean time for evaluation was significantly shorter in the knowledge group (1:58 h +/- 0:50 vs 2:53 h +/- 0:50, P = .004). Incidence of spontaneous preterm birth (SPTB) in the knowledge group was significantly reduced (13.0 vs 36.2%, P = .01). The knowledge of CL and FFN was associated with reduction in length of evaluation in women with CL > or = 30 mm and in incidence of SPTB in all women with PTL.