AbstractObjectiveTo study if a repeat cervical length (CL) measurement in the patient already diagnosed with a short cervix has any additional value in the prediction of preterm delivery.Study designThis was a retrospective study of singleton pregnancies with cervical lengths 1–25 mm at a gestational age of 16–28 weeks seen in our institution between 2002 and 2005. Patients who were managed expectantly and had a follow‐up CL measurement within 3 weeks were included. Delivery data were obtained from the patients' computerized medical records.ResultsSixty‐eight patients met the inclusion criteria. 37% of the patients had a shorter CL on the second measurement. These patients delivered at an earlier gestational age (36 + 4 vs. 38 + 2 weeks, P = 0.031) and were more likely to deliver at < 37 weeks (60% vs. 26%, P = 0.009). The change in the CL correlated with earlier gestational age at delivery and delivery at < 37 weeks.ConclusionIn patients diagnosed with a short cervix, follow‐up CL measurement is a strong predictor of preterm delivery. Greater change in the CL correlates with an earlier gestational age at delivery. In the patient diagnosed with a short cervix, a repeat measurement of CL gives additional predictive value. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.