Quantitative T2* mapping in the developing brain is challenging due to inherent motion of fetal and neonatal subjects. This study uses a motion robust framework for acquisition, reconstruction and segmentation of whole brain T2* maps. This is achieved by single-shot multi-echo GRE EPI acquisition, multi-level slice-to-volume registration and gestational-age specific brain atlas segmentation. T2* values are reported for fetal and neonatal subjects at 3T. Findings indicate large variability in T2* within each subject group, non-linear change in T2* between fetal and preterm neonatal period, and significantly higher mean T2* constants than previously reported in adult subjects.