[Obstetric conjugate diameter (conjuata vera obstetrica). New results obtained via ultrasonic measurements during pregnancy (author's transl)].

The obstetric conjugate diameter can be measured by means of ultrasonic devices, particularly those with slow production of the ultrasonic image (Kretz and others). The mean value of the conjugata vera obstetrica was 11.7 cm in the 382 measurements conducted by the authors. With 7.85% of the measurements, the obstetric conjugate diameter was below 11.0 cm. This means that a narrowed pelvis due to a shortened obstetric conjugate diameter was a relatively frequent occurrence, basing on a biparietal pelvic diameter of 10 cm at the time of delivery. During pregnancy and repeat pregnancy, no clinically significant increase of the obstetric conjugate diameter can be found. Ultrasonic examination is very suitable as a screening method to detect and identify complications in the mechanism of birth well in time before the onset of labour. The technique can be acquired relatively easily. Measurements are reproducible at any required rate, and will not disturb or molest the pregnant women. It does not involve any radiological load. Nevertheless, ultrasonic examination cannot be considered as the full successor to the x-ray film. In particular, lateral x-ray examination is still important in case of clinical suspicion of a "long pelvis" (according to Kirchhoff) or the rare forms of contracted pelvis, if a complication of the birth mechanism cannot be excluded despite normal obstetric conjugate diameter.