A Sodium valproate.

[Feedback :- The use of this medication is known to increase the risk of neural tube defects.]

B Thiamine.

[Feedback :- Only folic acid supplementation has been shown to decrease the incidence of neural tube defect.]

C Folic acid.

This is the Correct Answer

[Feedback :- Preconceptual administration of folic acid decreases the incidence of neural tube defects in at-risk women by as much as 75%.]

D Ultrasound screening.

[Feedback :- Ultrasound screening has led to a decrease in the number of babies being born with neural tube defects (due to an increase in the number of terminations), but this is obviously performed after pregnancy has already occurred and will not decrease the absolute risk.]

E Vitamin B₁₂.

[Feedback :- Only folic acid supplementation has been shown to decrease the incidence of neural tube defect.]