**Core Concept**
The question is testing the concept of recurrence risk in neural tube defects (NTDs), specifically open spina bifida, and the association with maternal folic acid supplementation. Neural tube defects are birth defects of the brain or spine that happen in the first month of pregnancy, often due to genetic or environmental factors.

**Why the Correct Answer is Right**
A mother who has previously delivered a baby with an open neural tube defect is at higher risk of having another child with a similar defect. This is because the genetic predisposition to NTDs is higher in families with a history of such defects. Folic acid supplementation is crucial in reducing the recurrence risk. When taken before and during early pregnancy, folic acid can significantly decrease the likelihood of having another child with a neural tube defect.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not address the relationship between maternal folic acid supplementation and the risk of recurrence of NTDs.

**Option B:** This option is incorrect because it is too vague and does not provide any specific information about the relationship between maternal history and recurrence risk of NTDs.

**Option C:** This option is incorrect because it suggests that the only factor influencing the risk of recurrence of NTDs is the mother's age, which is not the case.

**Clinical Pearl / High-Yield Fact**
It is essential for pregnant women with a history of giving birth to a child with a neural tube defect to take folic acid supplements before and during early pregnancy to significantly reduce the recurrence risk.

**Correct Answer:** D.