Abstract: 

Obstetric forceps is an instrument that is frequently used when childbirth fails to progress. The forceps blades are shaped to fit perfectly around an average sized fetal head. If they are placed symmetrically then the normal stress and displacements to the fetal scalp will be minimal. In the case that they are placed asymmetrically relative to the fetal scalp bones, the normal stress and displacements can become unwieldy and when combined with the tangential force to extract the fetus this may cause significant trauma. To assess the effect of symmetric and asymmetric forceps placement, we have created mesh models of the fetal head and of a Neville-Barnes obstetric forceps. Three decimation levels were used for the fetal head with approx. 8K, 15K and 19K triangular shell elements (S3) to model the fetal scalp bones, fontanelles and sutures. The latter soft tissues were modelled using Mooney-Rivlin hyper-elastic material properties whereas the bones are orthotropic elastic. A fluid cavity was added to the fetal head to model the fetal brain’s incompressibility. The forceps blades were modelled using tetrahedral elements (C3D4) and are in stainless steel. ABAQUS standard dynamic analyses were run, using the Hilber-Hughes-Taylor numerical integration algorithm with general sliding contact between the blades and head, in two separate steps: closing the blades, and traction on the blades at different speeds. We observed that asymmetric placement can cause large local deformations that may cause potential damage to the fetal scalp and subsequently to blood vessels in the underlying fetal brain.

Presenter: 

Rudy Lapeer Associate Professor - University of East Anglia Dr. Rudy Lapeer is an Associate Professor at the School of Computing Sciences, University of East Anglia in Norwich. His research interests include from a wider perspective, the FEM and soft tissue modelling, and more specifically, the modelling of the complex mechanical process of childbirth. With his team, he developed in the last decade the BirthView “digital twin” that is capable of simulating childbirth as it happens in reality.