A woman has previously have 2 anencephalic babies. What is her RISK of having a third baby with anencephaly?
## **Core Concept**
The question revolves around the risk of recurrence of anencephaly, a type of neural tube defect (NTD), in a woman who has had two previous anencephalic babies. Anencephaly is a congenital anomaly characterized by the absence of a major portion of the brain, skull, and scalp. It results from the failure of neural tube closure during early embryonic development.
## **Why the Correct Answer is Right**
The risk of recurrence of anencephaly or other NTDs in a family is known to be higher than in the general population. For a woman who has had two previous children with anencephaly, the risk of having a third child with an NTD is significantly increased. Studies suggest that the risk of recurrence after having one affected child is about 3-5%, after two affected children, the risk increases to about 10-20%, and after three, it can be as high as 30% or more. This increased risk is attributed to both genetic and environmental factors.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a risk similar to or only slightly higher than the general population risk of NTDs, which is typically around 0.5-1 per 1,000 births. Given the history of two anencephalic babies, this risk seems too low.
- **Option B:** While this option indicates a higher risk than the general population, it does not sufficiently account for the increased risk associated with having had two previous anencephalic babies.
- **Option D:** This option suggests a risk that might be considered too high even for someone with a significant family history of NTDs, though risks can vary based on multiple factors.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that folic acid supplementation before conception and during early pregnancy significantly reduces the risk of neural tube defects. For women who have had a previous pregnancy affected by an NTD, the recommended dose of folic acid is higher (usually 4 mg/day) than for those at low risk. This is a critical preventive measure.
## **Correct Answer: C.**