CPD is best assessed by

Methods of assesment of Pelvis  Clinically Imaging studies Clinical Pelvimetry : Done manually Can be done beyond 37th week, better done after onset of labour Following are to be observed  Sacrum  Sacrosciatic notch Iscial spines  Side walls Pubic arch Pubic angle Transverse diameter of outlet Imaging : X-ray pelvimetry  USG CT  MRI X-ray pelvimetry :  Limited value in diagnosis Can only assess size and shape of pelvis  Useful in cases with pelvic fractures  Disadvantage : Radiation exposure to both mother and foetus (885 milirad) Erect lateral view  CT  Easier to perform Radiation exposure(45-425milirad) More accurate MRI More accurate to assess bony pelvis Assess pelvic capacity in different planes Assess foetal size and head volume, pelvic soft tissues No radiation risk Expensive,limited availability, more time taking USG :  Accurately measures the biparietal diameter