This study aims to evaluate a prototype device detecting zinc protoporphyrin-IX fluorescence non-invasively from the intact oral mucosa. Zinc protoporphyrin-IX is an established indicator of iron deficiency. The prototype device is used to measure the erythrocyte zinc protoporphyrin-IX/heme ratio for women after delivery, a study group chosen because of an elevated risk of iron deficiency. The results from the non-invasive measurements are compared to reference measurements of the erythrocyte zinc protoporphyrin-IX/heme ratio from residual blood samples from the same patients and to other indicators of iron status, including hemoglobin, ferritin, serum iron, transferrin, transferrin saturation and soluble transferrin receptor.