Simulating birth to investigate clinician-applied loads on newborns

This report describes the design, development and testing of a force-measuring birth simulator. Designed to mimic the feel of an obstetric emergency, the simulator is named shoulder dystocia birth model (SDBM). The SDBM consists of a simply supported overhung beam, instrumented with two strain gauges and one commercially-available sensor, all of which are embedded in a maternal manikin that rests on a height-adjustable scissors jack. Rigidly affixed to the free end of the beam, a model of a newborn head protrudes from the manikin to allow physicians to simulate the loads they exert when delivering a newborn. A microcomputer-based data acquisition system monitors, analyses and processes the output from the gauges and the sensor in real time. The system measures axial force and vertical force to within 2% accuracy and the end-moment to within 5% accuracy. Testing with 15 University of Maryland clinicians simulating routine, difficult and SD deliveries reveals average peak force magnitudes of 68 N, 118 N and 172 N and average peak moment magnitudes of 138 N.cm, 384 N.cm and 621 N.cm, respectively. The standard deviations for these average peak values are large indicating wide variation in perceived loads required to deliver. Confirming clinical observation, average peak forces for some difficult and many shoulder dystocia deliveries exceed the force necessary to induce clavicle fracture at birth.