Objectives: To compare the incidence of dynamic cervical change (spontaneous real-time cervical shortening) in singleton patients with and without symptoms of preterm labor (PTL). Methods: A total of 109 patients between 23 and 34 weeks' gestation with and without PTL symptoms underwent cervical length ultrasound and contraction monitoring over a 10-min period. Cervical length measurements were taken at 1-min intervals. Exclusion criteria included ruptured membranes, dilation > 3 cm or cerclage, following the examination, the sonographer made a subjective assessment as to whether noticeable dynamic cervical change had occurred. A measurement was then made during the application of fundal pressure. The initial cervical length, shortest length, maximum change in length and incidence of dynamic change were compared between patients with and without PTL symptoms. The shortest cervical length was compared to the presence and timing of uterine contractions and the measurement during the application of fundal pressure. Results: A total of 43 asymptomatic patients and 66 symptomatic patients were studied. Compared to asymptomatic patients, patients with PTL symptoms had shorter initial lengths, nadir lengths and mean lengths over time as well as a greater amount of maximum change. Dynamic cervical change was more frequently seen in symptomatic patients (48% vs. 9%, P < 0.001) and was associated with uterine contractions (odds ratio 4.6, 95% CI 1.9-10.8). Fundal pressure was not able to reproduce the shortest cervical length that occurred spontaneously during the observation period. Conclusions: Dynamic cervical change (real-time cervical shortening) is common in patients with PTL symptoms and is associated with uterine contractions. Whether this finding enhances the ability to predict preterm delivery remains to be elucidated. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.