Pelvic contraction Birth canal bony canal Soit cana abnormal bony canal: pelvic contraction any contraction of the pelvic diameters that diminishes the capacity of the pelvis can creat dystocia during laborPelvic contraction Birth canal – bony canal – soft canal abnormal bony canal: pelvic contraction – any contraction of the pelvic diameters that diminishes the capacity of the pelvis can creat dystocia during labor