North American Registry of Midwives (NARM) Practice Exam

What is the primary cause of macrocytic anemia?

1. Iron deficiency

2. Vitamin B12 deficiency

3. Chronic disease

4. Leukemia

The correct answer is: Vitamin B12 deficiency

Macrocytic anemia is primarily characterized by the presence of large red blood cells (macrocytes) in the bloodstream, which results from impaired DNA synthesis during red blood cell production. The most common causes of macrocytic anemia are deficiencies in specific vitamins, particularly vitamin B12 and folate. Vitamin B12 deficiency leads to inadequate production of red blood cells, specifically affecting the maturation of these cells in the bone marrow. Without sufficient vitamin B12, the red blood cells cannot divide properly, resulting in the production of larger cells. This condition can arise from various factors, including insufficient dietary intake, malabsorption issues due to gastrointestinal disorders, or pernicious anemia, where the body cannot absorb vitamin B12 due to a lack of intrinsic factor. In contrast, iron deficiency anemia generally leads to microcytic red blood cells (smaller than normal), chronic disease anemia is often normocytic, and leukemia, while it can affect the number and function of blood cells, is not classified under macrocytic anemia. Thus, vitamin B12 deficiency stands out as the primary cause of macrocytic anemia, explaining why it is the correct answer to this question.