This change in the angle of the femoral head gives the female gait its characteristic (i.e. swinging of hips).

http://en.wikipedia.org/wiki/Pelvis

The acetabula are wider apart in females than in males.In males, the acetabulum faces more laterally, while it faces more anteriorly in females. Consequently, when men walk the leg can move forwards and backwards in a single plane. In women, the leg must swing forward and inward, from where the pivoting head of the femur moves the leg back in another plane. This change in the angle of the femoral head gives the female gait its characteristic (i.e. swinging of hips).