**Core Concept**
Repair of the cleft of the hard palate is a crucial aspect of orthognathic surgery and maxillofacial reconstruction. The ideal time of repair is influenced by factors such as the size and location of the cleft, the age of the patient, and the presence of any associated anomalies.

**Why the Correct Answer is Right**
The optimal time for repairing the cleft of the hard palate is between 9 to 12 months of age. This timing allows for the closure of the cleft before the child starts teething, which can help prevent dental malalignment and facilitate proper speech development. Additionally, repairing the cleft at this age enables the child to undergo subsequent orthodontic and orthognathic treatments more effectively. The repair is typically performed under general anesthesia, and the technique may involve the use of a two-stage approach, where the soft palate is repaired first, followed by the hard palate repair.

**Why Each Wrong Option is Incorrect**
**Option A:** Repairing the cleft of the hard palate at birth is not ideal due to the high risk of complications, such as bleeding and infection, in this age group.
**Option B:** Waiting until the child is 18 months old or older may lead to speech difficulties and dental malalignment.
**Option C:** Repairing the cleft of the hard palate in the second year of life may not be feasible due to the child's increasing mobility and potential for complications.

**Clinical Pearl / High-Yield Fact**
It is essential to repair the cleft of the hard palate before the child starts teething to prevent dental malalignment and facilitate proper speech development.

**Correct Answer: C. Between 9 to 12 months of age.**