Although the activity and expression of HSD11B-2 within the placenta correlates with birth weight [14,15] and HSD11B-2 gene expression is reduced in IUGR rats and human gestations [14,16], relative changes in HSD11B-1/2 activity/expression cannot fully characterize the amount of active/inactive GCs within the placenta as there is an influx of GCs from maternal [17] and fetal [18] compartments to the placenta during pregnancy. This evidence concerns the gene HSD11B2 and fetal growth restriction.