**Core Concept**
Hydrocephalus is a condition characterized by an accumulation of cerebrospinal fluid (CSF) within the brain, leading to increased intracranial pressure and potentially causing damage to the brain tissue. Antenatal diagnosis of hydrocephalus is crucial for appropriate management and planning.

**Why the Correct Answer is Right**
Antenatal diagnosis of hydrocephalus is typically done through ultrasonography, which allows for visualization of the fetal brain and measurement of the ventricular size. This imaging modality is particularly useful in the second trimester of pregnancy. The ventricles are measured to assess for any dilation, which is indicative of hydrocephalus.

**Why Each Wrong Option is Incorrect**
**Option A:** Magnetic Resonance Imaging (MRI) is not commonly used for antenatal diagnosis of hydrocephalus due to its limited availability, higher cost, and potential risks associated with the procedure.
**Option B:** Computed Tomography (CT) is not typically used in pregnancy due to the high radiation exposure, which can be detrimental to the developing fetus.
**Option C:** Amniocentesis is a procedure used to diagnose genetic disorders and infections, but it is not used for the diagnosis of hydrocephalus.

**Clinical Pearl / High-Yield Fact**
Ultrasonography is a safe and effective method for antenatal diagnosis of hydrocephalus, and it should be performed in a center with experience in fetal imaging to ensure accurate results.

**Correct Answer:** C. Ultrasonography is typically used for antenatal diagnosis of hydrocephalus.