This is sooooo common in pregnancy - some women can be taking all the supplements and the right foods but to no avail. Some doctors make such a big song and dance about it, but yes there are two things they measure, spelling I am not sure of but ferritin (SP?) and haemoglobin. A client's mother is a chemist and actually explained to the midwife what the results actually meant, as they were complaining she had low iron, but it wasnt a problem in reality.