['To investigate whether the degree of change in cervical length during a uterine contraction is predictive of subsequent progression of labor.', 'The subjects were 73 uncomplicated parturient women at term. We observed the cervix before, during and after a uterine contraction by transvaginal ultrasound in the first stage of labor and determined the degree of cervical shortening during the contraction relative to the cervical length before contraction. We related the degree of cervical shortening to labor patterns at the time of the ultrasound examination, which were retrospectively determined by reviewing the partogram.', 'The cervix was shortened in length by about 50% on average during a uterine contraction in the normal course of labor. The degree of cervical shortening was significantly greater in the normal latent and active phases than it was in the prolonged latent phase, protracted active phase and false labor, whereas there were no differences between the former two phases nor between the latter three phases. Nulliparous and parous women exhibited almost the same degree of shortening in the normal latent and active phases.'] Is sonographic assessment of the cervix before , during and after a uterine contraction effective in predicting the course of labor?