Which embryologic fusion failure leads to a cleft palate (without cleft lip)?

• A. Failure of fusion of palatal shelves with each other and with the primary palate during weeks 7–12.
• B. Failure of fusion between maxillary process and medial nasal process.
• C. Abnormal development of the nasal septum.
• D. Overfusion of palatal shelves.

Answer: (A)

The main idea is how the palate forms and what happens when fusion fails. During early fetal development, the primary palate comes from the intermaxillary segment, while the secondary palate develops from the palatal shelves that arise on the maxillary processes. These shelves rotate upward, meet in the midline, and fuse with each other and with the primary palate to create a complete roof of the mouth. If this fusion fails during the critical period around weeks 7–12, a cleft palate develops without involving the lip.

This is different from a cleft lip with or without palate, which happens when the maxillary process fails to fuse with the medial nasal process, affecting the lip and sometimes the primary palate. Abnormal development of the nasal septum or excessive, or over, fusion wouldn’t produce the same gap in the palate described here.