## **Core Concept**
The question assesses the ability to identify congenital malformations that can be detected during the first trimester of pregnancy using ultrasound. This requires knowledge of fetal development and the timing of when various malformations can be identified.

## **Why the Correct Answer is Right**
Anencephaly is a severe congenital anomaly characterized by the absence of a major portion of the brain, skull, and scalp. It occurs due to the failure of neural tube closure during embryonic development. This condition can be detected as early as 10-14 weeks of gestation through ultrasound examination, making it one of the malformations identifiable in the first trimester.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain cardiac anomalies can be detected in the first trimester, they are generally more challenging to diagnose than anencephaly and often require more detailed examination and expertise.
- **Option B:** Cystic hygroma can indeed be detected in the first trimester. However, anencephaly is more readily identifiable and commonly associated with first-trimester ultrasound screening.
- **Option D:** Exomphalos (omphalocele) can also be detected in the first trimester but might be less commonly identified than anencephaly due to its smaller size and the technical limitations of early ultrasound.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that anencephaly is one of the neural tube defects (NTDs) that can be significantly reduced in incidence through folic acid supplementation before and during early pregnancy. Early detection through ultrasound allows for informed decision-making and planning for the pregnancy.

## **Correct Answer:** . Anencephaly