This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal Skull and Maternal Pelvis, Subject name: Gynaecology & Obstetrics
Most important diameter of pelvis during labour is: 
Select and explain. 
A. Interspinous diameter of outlet, B. Oblique diameter of inlet, C. AP diameter of outlet, D. Intertubercular diameter
A: Interspinous diameter of outlet
Answer: A: Interspinous diameter of outlet 
Explanation: Ans. is a, i.e. Interspinous diameter of the outletRef. Williams Obs. 24/e, p 33; Dutta Obs. 9/e, p 82Interspinous diameter is the distance between the two ischial spines and is the smallest diameter of the pelvis = 10 cm or slightly greater. It corresponds to the transverse diameter of midpelvis (i.e. plane of least pelvis dimensions).