This prospective observational study was to evaluate the efficacy of combining phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) and transvaginal ultrasound cervical length (CL) compared with either indicator alone in predicting pre-term labour (PTL). Women with singleton pregnancy between 24 and 36 weeks' gestation with evidence of PTL were subjected to phIGFBP-1 and CL tests. Of the 51 women, five were tested positive (phIGFBP-1 positive and CL <2.5 cm) for combination of phIGFBP-1 and CL (four delivered within 1 week), whereas 46 tested negative, of which, only one delivered. A much higher negative predictivity (NP), positive predictivity (PP) and specificity (SP) in the combination test was seen compared with phIGFBP-1 or CL alone (NP: 97.8% vs 97.7% vs 97.1%; PP: 80.0% vs 51.1% and CL 23.5%; SP: 97.8% vs 93.5% vs 71.1%, respectively). The cervical os dilatation of 2 cm with combined positive test (p = 0.001) indicated a higher likelihood of PTL.