Background: Because of numerous abnormalities of craniovertebral junction development observed in the prenatal period, the region has been studied thoroughly in order to elucidate the mechanism of axial differentiation, dependence of vertebral morphology on the development of ossifi cation centers
and the mechanisms regulating the dynamics of growth. AIM: Analysis of morphological changes of the craniovertebral junction taking place during the prenatal period by quantitative assessment of some developmental changes such as growth rate, sexual dimorphism, interdependence of the analyzed parameters, taking into consideration the variable geometry of the studied area.
Material/Methods: The study was carried out on 48 fetuses (22 male, 26 female) of 86-212mm crown-rump length(CRL) range. The applied methods included: anthropometry, precise measurements, as well as
trigonometric calculation of angles.
Results: All the investigated parameters demonstrated a strong, statistically signifi cant correlation with CRL.No statistical signifi cance of sexual dimorphism and differences between left- and right-sided measurements was demonstrated. The development rate indexes for the height of C1,C2 posterior vertebral
arches, unlike those for the transversal dimensions of C1,C2 posterior vertebral arches, decrease
after 5 months of gestational age. Little variability of the angles determined by geometrical
reconstruction evidences close interdependence in the development of the analyzed craniovertebral
junction elements.
Conclusions: Geometrical confi guration of the craniovertebral junction during the fetal period is constant, with growth isometry preserved throughout intrauterine development. The occipital bone and C1, C2 cervical vertebrae are closely correlated according to structural and functional dependences.

Keywords: Cervical Vertebrae - embryology, Anthropometry, Fetus - anatomy & histology, Occipital Bone - embryology, Pregnancy