Can a 15-mm cervical length cutoff discriminate between low and high risk of preterm delivery in women with threatened preterm labor?

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 <15 mm in 36 women (24.7%) and ≥15 mm in 110 women (75.3%). Spontaneous delivery occurred within 48 h or 7 days of presentation and before 34 weeks in 25, 38.9 and 50.0% of women with CL <15 mm and 3.6, 9.1 and 11.8% of women with CL ≥15 mm, respectively. The 15-mm CL cutoff had a sensitivity, false positive rate and negative predictive value for delivery within 48 h of 69.0, 20.3 and 96.4%, and within 7 days of 58.3, 18.1 and 90.9%. Women with CL <15 mm had odds of delivery within 7 days of 6.4 (95% CI 2.5-16.2).

CONCLUSION

Although a 15-mm CL defines a group of women at high risk of spontaneous preterm delivery, 10 out of 110 women (9.1%) with a CL ≥15 mm deliver within 7 days.