Fetal head molding: An investigation utilizing a finite element model of the fetal parietal bone

Abstract

Fetal head molding is the change in head shape due to the forces of labor. Previous investigations of the molding process have been largely qualitative in nature. In order to provide a first step toward a quantitative description of the deformations of the fetal head, a finite element analysis of the parietal bone of the fetal skull is performed. The structural geometry of the bone is derived from orthogonal radiographs of a full term anatomical specimen. Load and material parameters are taken from previous investigations. The bone is modeled using 63 thin shell elements from the SAP IV element library. Scaled models of preterm parietal bone are compared to term bone models.The results indicate that the models undergo deformations which are qualitatively similar to those seen in normal labor. The preterm parietal bone model exhibits deformations 2-4 times greater than the term bone model for the same load distribution. The significance of these results and their relationship to the molding process are discussed.