Although the essential role of iron during pregnancy is well established, concerns have been raised that current iron supplements given routinely during pregnancy may also have harmful consequences, such as increased oxidative stress and enhanced risks of infection, pre-eclampsia and impaired glucose regulation. A potential mechanism for the production of adverse effects is the appearance of non-transferrin-bound iron after oral administration of iron supplements. Non-transferrin-bound iron is more readily available to pathogens and could promote injurious free radical reactions that might add to the oxidative stress of pregnancy.

The present study will determine if oral administration of 60 mg of iron as ferrous sulfate during the second trimester of pregnancy is followed by the appearance of non-transferrin-bound iron two hours later. The investigators will examine the influence of a variety of factors, including iron status and previous use of iron supplements. Detection of non-transferrin-bound iron after administration of an iron supplement to pregnant women would be an important new observation that could lead to re-evaluation of current methods of iron supplementation.

Inclusion Criteria:

• Pregnant woman
• Age 18 to 45 years
• singleton pregnancy
• between 24 and 28 of gestation (at study day)
• regular visits at prenatal clinic
• capability and willingness to comply with study protocol
• voluntary signed informed consent

Exclusion Criteria:

• Multiple pregnancy
• Acute or chronic disease or disorder
• Incapability of following the study protocol
• Homelessness
• Active drug/alcohol dependence or abuse history
• Currently participating in another clinical trial or having participated in another clinical trial during the last 3 months prior to the beginning of this study