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
Target magnesium level when used for eclampsia prophylaxis 
Select and explain. 
A. 4.8 → 8.4 mg / dL, B. 2.0 → 4.0 mg / dL, C. 8.4 → 10.0 mg / dL, D. None of the above
A: 4.8 → 8.4 mg / dL
Answer: A: 4.8 → 8.4 mg / dL 
Explanation: Serum magnesium levels are measured at 4 → 6 hour and adjusted to maintain levels between 4 and 7m Eq / L .