This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Gynaecology & Obstetrics
Dose of folic acid for women at increased risk of Neural tube defects preconceptionally is 
Select and explain. 
A. 4ng, B. 4mcg, C. 4mg, D. 4g
C: 4mg
Answer: C: 4mg 
Explanation: Most women at increased risk for NTDs benefit from 4 mg folic acid taken daily before conception and through the first trimester. This is paicularly impoant if a woman has one or more prior affected children or if either the pregnant woman or her paner has such a defect. Folic acid supplementation may not decrease the risk for NTDs in those with valproic acid exposure, pregestational diabetes, first-trimester fever or hot tub exposure, or defects associated with a genetic syndrome (Ref: William's Obstetrics; 25th edition)