SLC38A7 and fetal growth restriction: For instance, serine and glutamate/glutamine absorption can promote the absorption of serine and glutamic acid, while absorption of branched-chain amino acids can actually reduce the absorption of threonine, histidine, and lysine.13,14 Newborns with IUGR who weigh less than the 3rd percentile show significantly reduced amino acid concentrations, which may be related to impaired function of the placental amino acid transporters.12