This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Which of the following is the most sensitive for detection of iron depletion in pregnancy: March 2013 
Select and explain. 
A. Serum iron, B. Serum transferrin, C. Serum erythropoitein, D. Serum ferritin
D: Serum ferritin
Answer: D: Serum ferritin 
Explanation: Ans. D i.e. Serum ferritin