Objectives: To investigate if a cervical length (CL) cutoff of 15 mm is relevant to use in women with threatened preterm labor. Methods: From 2006 to 2009, 146 women with singleton pregnancies were admitted with threatened preterm labor between 23 and 33+6 weeks of gestation at Copenhagen University Hospital. Transvaginal sonographic measurement of CL was carried out on admission. Outcome measures were spontaneous delivery within 48 h, within 7 days and delivery before 34 weeks according to a CL cutoff of 15 mm. Results: CL was