Asked by Anonymous
- Antero -posterior diameters:
- Anatomical antero-posterior diameter (true conjugate) = 11cm
- from the tip of the sacral promontory to the upper border of the symphysis pubis.
- Obstetric conjugate = 10.5 cm
- from the tip of the sacral promontory to the most bulging point on the back of symphysis pubis which is about 1 cm below its upper border. It is the shortest antero-posterior diameter.
- Diagonal conjugate = 12.5 cm
- i.e. 1.5 cm longer than the true conjugate. From the tip of sacral promontory to the lower border of symphysis pubis.
- External conjugate = 20 cm
- from the depression below the last lumbar spine to the upper anterior margin of the symphysis pubis measured from outside by the pelvimeter . It has not a true obstetric importance.
- Anatomical antero-posterior diameter (true conjugate) = 11cm
- Transverse diameters:
- Anatomical transverse diameter =13cm
- between the farthest two points on the iliopectineal lines.
- It lies 4 cm anterior to the promontory and 7 cm behind the symphysis.
- It is the largest diameter in the pelvis.
- Obstetric transverse diameter:
- It bisects the true conjugate and is slightly shorter than the anatomical transverse diameter.
- Anatomical transverse diameter =13cm
- Oblique diameters:
- Right oblique diameter =12 cm
- from the right sacroiliac joint to the left iliopectineal eminence.
- Left oblique diameter = 12 cm
- from the left sacroiliac joint to the right iliopectineal eminence.
- Sacro-cotyloid diameters = 9-9.5 cm
- from the promontory of the sacrum to the right and left iliopectineal eminence, so the right diameter ends at the right eminence and vice versa.
- Right oblique diameter =12 cm
Further reading: https://epomedicine.com/medical-students/female-pelvis/