Development of the basilar part of the occipital bone in normal human fetuses.

The present study aims to investigate the normal maturity and growth of the basilar part of the occipital bone evaluated radiographically and histochemically during the first half of prenatal life. The material consisted of cranial bases from 49 normal human fetuses and, in addition, three separate occipital bones deviscerated from normal fetuses. The normal development of the basilar part of the occipital bone was divided into five maturity stages (OB-I to OB-V). Microscopic investigation confirmed the macroscopic findings described. For each stage the ventro-dorsal dimension of the occipital bone component was measured (LEN). The stages of (OB-I to OB-V) were related to gestational age (AGE), crown-rump length (CRL), LEN, and to the length of the humeral bone (HL). Close accordance was registered between OB stages and length values of the basilar part of the occipital bone, LEN, and length of the humeral bone, HL. A highly significant positive correlation was found between LEN and the parameters AGE, CRL, and HL values (P < 0.001). Standards for normal development of the basilar part of the occipital bone are considered important for evaluation of the pathological prenatal development of the cranial base.