Blood tests for iron at 28 and 36 weeks
Blood tests for iron (and others) are usually done as part of your
first pregnancy check-up visit at around 12 weeks of the pregnancy. However, they may be performed as early as 5 to 6 weeks of the pregnancy, if you see your local doctor before then (and they decide to take blood), or as late as 14 to 16 weeks if you take your time in seeing someone about your pregnancy care.
There are a few blood tests that caregiver's can use to test for iron deficiency and anaemia during pregnancy. However, only one or two tests tend to be used routinely because pregnancy changes can affect some of the results of others. Iron deficiency develops in three stages (over several weeks or months) therefore, different tests tend to be more useful than others at different times.
Blood tests for iron are usually taken by withdrawing a sample of blood from your arm and sending it to the laboratory for analysis. The results may be back within hours or a day or two. In some countries, where the haemoglobin test is performed at every pregnancy visit, a drop of blood may be taken by doing a finger prick to test (similar to the way it may be tested before you donate blood at the blood bank). This is a quick test that takes only minutes.
The body's path to iron deficiency is a slow one (usually over weeks or months) and can be broken down into 3 different stages, which are explained as follows:
Stage 1
Stage 2
Stage 3
Stage 1.In the early stages of iron deficiency a person starts to lose their iron stores from their liver, spleen and bone marrow. This can be detected by a blood test that looks at your 'serum ferritin'. A low serum ferritin is reflective of low iron stores and is regarded as the most valuable test in assessing a person's iron status (even before their haemoglobin level starts to fall and they are regarded as 'anaemic'). As a guide, whether you are pregnant or not,
A normal serum ferritin is:20 - 150 ng/ml