Which among the following is the smallest diameter of the pelvis in the midplane?
The smallest diameter of the midpelvis or midplane is the transverse or interspinous diameter (10cm or more) which is between the two ischial spines. True conjugate (obstetric conjugate) is the distance between the midpoint of the sacral promontory to prominent bony projection in the midline on the inner surface of the symphysis pubis. Diagonal conjugate is the distance between the lower border of symphysis pubis to the midpoint on the sacral promontory. The transverse or inteuberous diameter is the distance between the inner borders of the ischial tuberosities. Ref: Clinical Obstretics (10Th Edn.) By S. Gopalan, Sarala & Jain, Vanita (eds.), 2005, Page 5; Clinical Obstetrics 10th edition by S. Gopalan, Sarala & Jain, Vanita Page 4, Manual of Obstetrics, 3e by Shirish N Daftary Page 11-12; Manual of Obstetrics, 2nd Edition by Daftary, Page 16-18; Williams's obstetric, 22nd edition, Page 34
Interspinous diameter
True conjugate
Diagonal conjugate
Inteuberous diameter