The cause is usually Inadequate dietary intake (especially in adolescent girls) A previous pregnancy The normal recurrent loss of iron in menstrual blood (which approximates the amount normally ingested each month and thus prevents iron stores from building up) before the woman became pregnant Diagnosis of Iron Deficiency Anemia in Pregnancy Measurement of serum iron, ferritin, and transferrin Typically, Hct is ≤ 30%, and MCV is < 79 fL.