Abstract
In recent years a high accuracy in measuring the biparietal diameter by ultrasonography has been achieved. As this is only one parameter in forecasting cephalo-pelvic disproportion a study was made to determine whether the true conjugate can be measured by utrasound with approximately the same reliability as the biparietal diameter. First, one-dimensional ultrasound studies were compared with X-ray measurements. Later, equipment was used which allows simultaneous display on two oscilloscopes of the B-scan for orientation and the A-mode trace for exact measurement. To exclude disproportion in the mid-pelvis a vaginal / rectal probe was constructed. In longitudinal scans, information about the form of the birth canal is obtainable. Transverse scans performed at the level of the symphysis provide information on the pelvic entrance. To evaluate ultrasonic pelvimetry the outcome of labour in 246 cases was analysed. The study demonstrates that ultrasonic pelvimetry can be an invaluable supplementary aid to X-ray diagnosis of cephalo-pelvic-disproportion especially in cases of breech presentation. Because it is often possible to diagnose cephalo-pelvic disproportion conclusively by using ultrasonic pelvimetry, X-ray examination can be restricted to borderline cases. In this manner it is possible therefore to reduce radiation dosage.