BACKGROUND: This study examines the influence of prematurity and diabetes (DM) in pregnancy on metabolite patterns at birth, and associations with adiposity development in a prospective cohort. METHODS: Term and preterm (30-36 weeks gestational age [GA]) infants were enrolled and body composition assessments completed through discharge. Targeted metabolomics was used to assess metabolites in cord or infant blood in the first 2 days. RESULTS: Among 91 infants, 62 were preterm and 27 were exposed to DM. In factor analysis, variation in acylcarnitines' and non-essential amino acids differed by GA and DM exposure and were associated with adiposity at term age. DM-group had 1.95-fold increase in t4-OH-pro (p = 0.003) and 2.14-fold increase in taurine (p = 0.004) compared with non-DM group. Preterm infants had 1.77-fold increase in glycerophospholipid PC aa C32:2 versus term group (p <
0.001). Pathway analysis revealed differences across DM and GA groups in pathways associated with citrulline metabolism, amino acid transport/ synthesis, and fatty acid quantity/transport. CONCLUSION: In this cohort of infants, there are unique metabolite signatures associated with DM exposure, prematurity, and adiposity development after birth. These markers may reflect early metabolism changes in the developing infant which relate to known risks of adverse growth and cardiometabolic outcomes in this group. IMPACT: In this study of term and preterm infants, diabetes in pregnancy was associated with unique metabolic signatures at birth, including increased expression of metabolites related to protein synthesis and lipid metabolism. Metabolites related to lipid and protein metabolism were associated with adiposity development at term age, including estimated body fat percent, skin fold thickness measures, and arm circumference measures. Unique signatures of metabolites associated with prematurity and exposure to diabetes in pregnancy may reflect early metabolism changes in the developing infant which relate to known risks of adverse growth and cardiometabolic outcomes in this group.