This trial is a proof-of-concept study using a prototype fiber optic fluorometer to acquire autofluorescence spectra from women after delivery and determine the erythrocyte zinc protoporphyrin-IX fluorescence intensity from these spectra. The non-invasively determined fluorescence spectra are evaluated to provide a quantitative measure of the erythrocyte zinc protoporphyrin-IX/heme concentration ratio. These values are primarily compared to an erythrocyte zinc protoporphyrin-IX determined by HPLC from residual blood samples from the same subjects and secondarily to erythrocyte zinc protoporphyrin-IX/heme ratios determined using a commercial hematofluorometer (AVIV, model 206d) and other indicators of iron status, including hemoglobin, ferritin, serum iron, transferrin, transferrin saturation and soluble transferrin receptor