External conjugate

The external obstetric conjugate (Baudeloque’s diameter) is measured between the outer edge of the upper edge of the pubis and the posterior external point at the first sacral segment. Often, in the texts, the spinous process L5 is described as being the posterior landmark of the obstetric conjugate, but Baudeloque suggested to position the pelvimeter a little below the fifth lumbar spinous process: that means on the posterior border of the first segment of the sacrum (S1). The conjugate dynamically tested relates to the sacral nutation and contra-nutation movements.

Average measurement in female: about 200 mm.