Diameters of pelvis

Diameters of Pelvis :
1. INLET:
a) AP Diameter : Obstetric conjugate – 10-10.5 cm (This is calculated by subtracting 1.5 to 2 cm from Diagonal conjugate) (Also most important Diameter of pelvic Inlet (UPSC))
b) AP Diameter :

True conjugate – 11 cm

c) AP Diameter :
Daigonal conjugate – 12 cm (This can be measured clinically)

d) Oblique Diameter : 12 cm

e) Transverse Diameter : 13-13.5 cm

2. Mid PELVIS :

a) AP Diameter: 11.5 cm

b) Interspinous Diameter : 10 cm

3. OUTLET : a) AP Diameter : 9.5 – 11.5 cm

b) Intertuberous Diameter is : 11 cm

Fetal Skull Diameter : 1. Bimastoid diameter : 7.5 cm

2. Bitemporal diameter : 8 cm ----------- (Smallest diameter)

3. Super subparietal diameter : 8.5 cm

4. Biparietal diameter : 9.5 cm Transverse diameters of fetal skull is smaller than Transverse diameter .

AP diameters of fetal skull :

1. Suboccipito bregmatic (9.5 cm) – Complete Flexion (Attitude) – Vertex (presentation)
2. Suboccipito frontal (10 cm) – Incomplete Flexion (Attitude) – Vertex (Presentation)

3. Occipito-frontal (11.5 cm) – Marked deflexion (Attitude) – Vertex (Presentation)

4. Mento-Vertical (14 cm) – Partial extension (Attitude) – Brow (Presentation) ----(Longest diameter)

5. Sub-mento vertical (11.5 cm) – Incomplete extension (Attitude) – Face (Presentation)

6. Sub-mento bregmatic (9.5 cm) – Complete flexion (Attitude) – Face (Presentation)