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During certain clinical situations, some parturients require instruments for operative vaginal delivery, and various designs of vacuum extractors may affect the fetal head. To investigate the biomechanical effects of divergent sizes of silicone rubber vacuum extractors, we employed finite element analysis in this study. First, we constructed computer models for different vacuum extractor sizes (diameters: 40 mm, 50 mm, 60 mm, and 70 mm), flat surface, hemispherical ball, and fetal head shape. A hemispherical ball was the main design for the vacuum extractor model, and the material used for the vacuum extractor was silicone rubber. Next, the settings of 1 mm vacuum extractor displacement and vacuum cap pressure of 60 cmHg were applied. The main observation markers of this study were the respective von Mises stresses on the vacuum extractor and skull by the reaction force on the fixed end. The concluded results revealed that vacuum extractors with larger diameters lead to greater reaction force, stress, and strain on fetal heads. Therefore, this study’s biomechanical analytic consequences suggest that clinicians avoid selecting larger vacuum extractors during operative instrumental delivery so that fetal heads will experience less external force, deformation, and resultant complications. It could also provide a practical reference for obstetricians for instrumental vaginal delivery with the vacuum extractor made of silicone rubber. Full article

Operative delivery requires the use of a vacuum extractor; obstetricians can choose the appropriate vacuum extractor to make the delivery process smoother and safer. However, there is no biomechanical literature focused on the imposed effects of a vacuum extractor prepared with different materials and vacuum pressure on the fetal head during the process of delivery. Therefore, we first established and performed the finite element analytical model to explore the influences of vacuum extractors manufactured from different materials on the fetal head under various extractive pressures. The model of the vacuum extractor was designed as a hemispherical shape, and the material of the vacuum extractor was composed of silicone rubber and stainless steel for comparison. Four different vacuum pressures (500 cm H₂O, 600 cm H₂O, 700 cm H₂O, and 800 cm H₂O) were applied as the factors for investigation. The reaction force on the fetal head, von Mises stress of vacuum extractor, and von Mises stress on the skull of fetal head were measured and analyzed to evaluate the effects. The results revealed that subtle divergent influences of different vacuum pressures were observed, and the stainless-steel vacuum extractor induced a larger reaction force (358.04–361.37 N), accompanied with stress (13.547–13.675 MPa), on the fetal head than non-metallic or relatively softer materials. The results provide a reliable basis for selecting proper vacuum extractor during operative delivery to avoid obstetrical complications, such as scalp scratch, cephalohematoma and even intracerebral hemorrhage. Full article