has part has part occurs in characteristic of has modifier ossification Abnormal calvaria morphology Decreased skull ossification Decreased calvarial ossification A hypomineralised skull castes little or no acoustic shadow on prenatal ultrasound. This makes visualization of the intracranial anatomy clearer than normal. In conditions associated with profound hypomineralisation, the skull shape can be distorted by pressure from the ultrasound transducer later in pregnancy. abnormal decreased process quality vault of skull