Recommendations for diagnosis of iron deficiency in pregnancy recommend that all women be screened for iron deficiency and iron deficiency anaemia1. Monitoring of serum ferritin levels is considered the most useful and easily available method for assessing iron deficiency and levels should be checked early in pregnancy for women with risk factors for iron deficiency2. Serum ferritin levels less than 15 ng/dL are indicative of established iron deficiency while a level below 30 ng/dL in pregnancy indicates depleted iron stores and should prompt treatment with iron supplementation (see table below)3.
It should be noted that serum ferritin levels are increased in inflammatory states and may not be reflective of iron available for utilisation by the body. Consequently, concurrent measurement of markers for inflammation, including C-reactive protein and α1-acid glycoprotein, should be performed, and ferritin level thresholds for diagnosis of iron deficiency increased where inflammation is present3,4. A trial of oral iron is advocated as a diagnostic test for iron deficiency anaemia in pregnancy2, but oral absorption of iron is impaired in patients with inflammation or malabsorption of iron, meaning that this test is not conclusive in the event of failure to respond.
Levels of transferrin-bound iron represent the amount of iron available to the body and measure of the percentage of transferrin saturation with iron (TSAT) is advocated in chronic disease as a measure of iron levels not affected by inflammation5. At TSAT levels <15%, insufficient iron is delivered to bone marrow to sustain erythropoiesis, indicating iron deficiency (see table). Measurement of soluble transferrin receptor levels is an alternative method of monitoring iron deficiency, although there is limited data for this marker in pregnant women2.
Table 1. Indicators of the sequential stages of iron deficiency in women4