The measurements of the pelvic inlet can be described using the following diameters:

Anatomical transverse diameter
- Between: extreme lateral points of the pelvic inlet
- Average length: 5.1 - 5.3 inches (13 - 13.5 cm; largest diameter)
Right and left oblique diameters
- From: sacroiliac joint
- To: iliopubic (iliopectineal) eminence of the opposite side
- Average length: 4.7 - 4.9 inches (12 - 12.5 cm)
Right and left sacrocotyloid diameters
- From: middle of the promontory
- To: iliopubic (iliopectineal) eminence of the same side
- Average length: 3.5 - 3.7 inches (9 - 9.5 cm)
Anatomical (true) conjugate
- From: middle of the promontory
- To: superior border of the pubic symphysis, superior pubic ligament
- Average length: 4.3 inches (11 cm)
Obstetric conjugate
- From: middle of the promontory
- To: most bulging point on the back of the pubic symphysis about 0.4 inches (1 cm) below its superior border
- Average length: 3.9 - 4.1 inches (10 - 10.5 cm; it is the shortest anteroposterior diameter)
Diagonal conjugate
- From: middle of the promontory
- To: inferior border of the pubic symphysis, inferior pubic ligament
- Average length: 4.7 - 4.9 inches (12 - 12.5 cm)

The final three conjugates belong to the anteroposterior diameters of the pelvic inlet.

Unlock with Premium

Pelvic inlet diameters