In the prediction of preterm delivery, funneling does not provide any significant contribution in addition to cervical length.

ABSTRACT

Cervical length is influenced by the degree of cervical curvature. The disparity of measurements between the internal and external os taken as a straight line or along the cervical canal increases with cervical length. However, this disparity may not have any clinical implications because at short cervical length (less than 16 mm) the cervix appears to be always straight.