A multifactorial fracture risk analysis and vacuum-assisted delivery simulation across gestational ages using CT-derived finite element modeling with probabilistic material analysis.

Fetal tissue properties, such as cranial stiffness, increase with gestational age, creating a potential risk of injury during vacuum-assisted delivery (VAD) for both the neonate and the mother. Using nonlinear CT-derived finite element models combined with uncertainty quantification, this study evaluated the biomechanical responses across a wide range of fetal tissue and scalp properties, as well as maternal pelvic tissues. Simulations indicate that as the fetal head stiffens, maximum principal stress on the cranium rises, suggesting an increased likelihood of fracture, particularly at term. Similarly, maternal tissues, including the pelvic floor muscles and perineum, experience higher stress and strain with advancing gestation, indicating a greater risk of overstretch and tearing, under the assumption of constant maternal tissue properties across gestational age. Global sensitivity analysis using a surrogate model identified tissue stiffness (Young's modulus) as the primary factor governing these predicted outcomes. These findings emphasize that individual biological variability, particularly fetal gestational age, should be considered in VAD procedures and provide a quantitative framework for assessing and mitigating potential injury risk to both mother and infant.