Cephalo-pelvic disproportion exists when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. This may be due to a small pelvis, a nongynecoid pelvic formation, a large fetus, or a combination of these factors. Certain medical conditions may distort pelvic bones, such as rickets or a pelvic fracture, and lead to CPD.
Transverse diagonal measurement has been proposed as a predictive method.