This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Pediatrics
When should folic acid supplementation start in order to be effective in preventing neural tube defects? 
Select and explain. 
A. As soon as pregnancy is diagnosed, B. Before the beginning of 2nd trimester, C. At least one month before conception, D. At least 1 week before conception
C: At least one month before conception
Answer: C: At least one month before conception 
Explanation: Ans. C. At least one month before conception* To be effective, folic acid supplementation should be started at least 1 month before conception, and continued through the first 2-3 months of pregnancy.* All women desirous of becoming pregnant should consume 400-800mg folic acid daily; the dose is 4mg/day in those having delivered a child with neural tube defect.