The accurate prediction of preterm births is a big clinical challenge within obstetrics. Most women who present with symptoms of preterm labour do not go on to deliver within one week and the majority will even deliver at term. Correct discrimination between women with a high and low risk of short-term delivery would enable targeted interventions and transfers to improve neonatal outcomes and would also reduce overtreatment and unnecessary health care costs. Fetal fibronectin (fFN) is the most commonly used biomarker in tests aimed predicting preterm birth. Merel Bruijn evaluates a qualitative and quantitative form of fFN test, the aim being to establish the best approach for individualised risk assessment.