Reproducibility of biparietal diameter measurements obtained with a real-time scanner

In 80 patients, multiple measurements of the fetal biparietal diameter were made during one examination using a real-time scanner equipped with a coded cephalometer. From the sets of data, the means and standard deviations for the group of 80 patients were calculated. In 80 per cent of cases, the individual standard deviations of the results were less than or equal to the estimated standard deviation of the group as a whole. The variability of measurement related to biparietal diameter was least in the range 59 to 83 mm. Comparison of the results obtained with the coded device and others obtained 'blind' does not reveal any significant advantage for the coded device.