The anterior fontanel is expected to close between which ages?

• A. 6 to 9 months
• B. 12 to 18 months
• C. 24 to 30 months
• D. 30 to 36 months

Answer: (B)

The timing of how long the anterior fontanel stays open reflects how the skull bones ossify as the brain grows. At birth the fontanel allows for passage through the birth canal and rapid brain expansion. The anterior fontanel typically remains open through the first year and most children have it closed by about 12 to 18 months. This window fits the pace of skull bone fusion during infancy. If closure happens earlier than that, it would be unusually fast; if it remains open past 18 months, it’s generally considered later than the typical pattern, though some variation can occur. The other ages—earlier than 12 months or well beyond 18 months—don’t match the usual range for this fontanel’s closure.