Isotopic Values of Prenatal Development: δ ¹³ C and δ ¹⁵ N Variation in Early‐Formed Human Tissues

These findings indicate that, in perinates, neonates, and young infants (> 4.5 months old), physiological conditions associated with different developmental stages and tissue turnover rather than diet govern collagen isotope variation. Ossicles predominantly archive mid prenatal physiology; deciduous dentin emphasizes late gestation (±immediate perinatal); long bone/rib integrates and dampens signals over a broader interval. This study recommends tissue-aware sampling and reporting when inferring maternal diet, fetal physiology, and early-life stress from collagen.