OP13.06: Can cervical length discriminate between low and high risk of preterm delivery in women with threatened preterm labour?

To investigate if a cervical length (CL) cut-off of 15 mm is relevant to use in clinical practice in women with threatened preterm labour. 146 women with singleton pregnancies and intact membranes were admitted with threatened preterm labour between 23–33 + 6 weeks of gestation at Copenhagen University Hospital from January 2006 to September 2009. Transvaginal sonographic measurement of CL was carried out on admission. Administration of corticosteroids, tocolytics and antibiotics was determined by the attending obstetricians. The outcome measures were spontaneous delivery within 48 hours and 7 days of presentation, and delivery before 34 weeks of gestation according to a CL cut-off of 15 mm. CL was < 15 mm in 36 women (24.7%) and ≥ 15 mm in 110 women (75.3%) (Table 1). The risk of delivery within 48 hours and 7 days of presentation, and before 34 weeks of gestation was six to eight-fold higher in women with a CL < 15 mm compared to the group with CL ≥ 15 mm. The 15 mm CL cut-off had a sensitivity, false-positive rate and negative predictive value for delivery within 48 hours of 69.0%, 20.3% and 96.4%, and within 7 days of 58.3%, 18.1% and 90.9%. Although a 15 mm CL defines a group of women at high risk of spontaneous preterm delivery, 9.1% of women with a CL ≥ 15 mm deliver within 7 days.