Spontaneous preterm birth is a leading cause of perinatal morbidity and mortality; however, accurate identification of women who will deliver prematurely after the onset of uterine contractions is still challenging, because less than 10% actually give birth within 7 days of presentation. Risk stratification in women with preterm contractions would allow targeting of interventions such as corticosteroids, magnesium sulfate, and maternal transfer to a perinatal center to those who will indeed deliver preterm. Moreover, unnecessary treatments associated with potential complications could be avoided in symptomatic women who are unlikely to deliver preterm. Fetal fibronectin testing and cervical length measurement are the most used methods to assess the risk of preterm birth among symptomatic women. Interventional studies in singleton gestations suggest that assessment of cervical length, unlike fetal fibronectin testing, improves diagnostic accuracy and leads to better perinatal outcomes.