Pars basilaris size to estimate fetal and young infant age using forensic post mortem CT imaging

Accurate determination of fetal or neonatal age is vital in forensic and medicolegal death investigations. The pars basilaris of the occipital bone, one of the earliest and densest ossification centers, is less susceptible to taphonomic alteration than other measurements, and exhibits predictable growth patterns. Utilizing post mortem computed tomography (PMCT), measurements of the pars basilaris - specifically its maximum length (ML) and maximum width (MW) - can be applied to validated regression models to estimate age. We retrospectively reviewed all fetal and stillbirth/neonate PMCT cases from our institution over the past eight years and identified nine cases with known or previously estimated ages. ML and MW of the pars basilaris were measured in thin maximum intensity projection reconstructions. Age predictions and 95% confidence intervals were calculated using published regression equations based separately on ML and MW. We also derived a combined model to yield a single age estimate with its corresponding confidence interval. In all nine cases, the predicted age intervals included the known or previously estimated age. The results indicate that pars basilaris biometry reliably estimates age using PMCT. Cases involving maternal conditions-such as diabetes, preeclampsia, and alcohol exposure-showed deviations from average pars basilaris growth but remained within statistical confidence limits. Pars basilaris biometry via standard PMCT protocols provides a straightforward method to approach fetal and early infant age estimation in forensic contexts. Although maternal and pathological factors can influence bone size, the combined ML/MW model is accurate within its 95% confidence bounds. Further research should validate these findings across diverse populations and investigate integration with additional growth markers.