Impact of parturition on iron status in nonanaemic iron deficiency

Iron-deficient nonanaemic parturients risk underdiagnosis as a result of the reliance on postpartum ferritin and haemoglobin as markers of iron status. Ferritin is an acute-phase protein whose levels increase during the inflammatory response, as occurs after delivery. Our aims were to evaluate the impact of parturition on iron status, erythropoiesis and the inflammatory response, and identify the optimal parameters and timing for diagnosing iron deficiency in the presence of postpartum inflammation.

Conventional parameters of iron status, erythropoiesis and the inflammatory response (serum ferritin, serum iron, transferrin saturation, C-reactive protein) were compared with more recent parameters [soluble transferrin receptors (sTfR), hypochromic red cells, reticulocyte indices] within 48 h either side of delivery in 64 iron-deficient nonanaemic women (defined by a prepartum serum ferritin < or =15 microg L(-1), and a pre- and postpartum haemoglobin of > or =11.0 g dL(-1) and > or =10.0 g dL(-1), respectively).

Mean sTfR decreased pre to postpartum from 7.3 to 5.8 microg mL(-1) (P<0.01), while mean serum ferritin increased from 9.7 to 16.9 microg L(-1) (P<0.01). Serum ferritin did not correlate with haemoglobin pre or postpartum (r=0.04, P=0.7; r=0.2, P=0.09), but a correlation persisted postpartum between hypochromic red blood cells and haemoglobin (r=-0.26; P<0.05). The percentage of hypochromic red cells remained virtually unchanged pre- and postpartum (4.0% vs. 3.8%; NS). Postpartum mean reticulocyte haemoglobin content (CHr) was 27.1 +/- 1.6 pg.

Iron status should be tested prepartum, in the absence of an inflammatory response, rather than in the early postpartum. A valuable additional parameter, where available, might be the hypochromic red cell percentage, which is virtually uninfluenced by the inflammatory response. Furthermore, hypochromic red cell percentage, CHr and sTfR can be helpful to differentiate between functional iron deficiency and depleted iron stores.