When Do Babies' Soft Spots (Fontanelles) Close?
The anterior fontanelle (the main soft spot on top of a baby's head) typically closes between 13-16 months of age, though normal closure can occur anywhere from 4 to 26 months. 1, 2
Normal Closure Timeline
Typical Progression
- At birth: The anterior fontanelle averages 2.1 cm in size 2
- 1 month of age: The fontanelle reaches its maximum size at approximately 2.2 cm 3
- 6 months: Only 3% of healthy infants have a closed fontanelle 3
- 12 months: Approximately 26.5% of fontanelles are closed 3
- 13.8 months: This represents the median time of closure 2
- 16 months: More than 50% of fontanelles are closed 4
- 24 months: Approximately 93% of fontanelles are closed 3, 4
Important Clinical Context
- The normal range for fontanelle closure is quite wide, spanning from 4 to 26 months of age 2, 5
- There are no gender differences in fontanelle size or closure timing 3
- Fontanelle size does not correlate with a child's weight, length, or head circumference 3
When to Be Concerned
Delayed Closure (Beyond 24 Months)
Delayed fontanelle closure beyond 24 months warrants evaluation for underlying conditions, including: 1, 2
- Hypothyroidism
- Down syndrome
- Achondroplasia
- Rickets
- Increased intracranial pressure
Other Abnormal Fontanelle Findings
- Bulging fontanelle: May indicate increased intracranial pressure or intracranial/extracranial tumors 2
- Sunken fontanelle: Usually indicates dehydration 2
Key Clinical Pearls
Normal Variants
- Early closure (5-6 months): Occurs in 3-5% of healthy infants and may represent a normal variant 4
- Persistent open fontanelle beyond typical ranges: Can be a normal outlier if all pathologic conditions have been ruled out 5, 6
- Wide variability in both timing and size among healthy infants is expected 4
Monitoring Considerations
- The anterior fontanelle serves as an acoustic window for brain ultrasonography before closure 1
- After fontanelle closure, CT and MRI become the primary imaging modalities for intracranial assessment 1
- Children receiving growth hormone therapy require head circumference monitoring, especially if fontanelles are open when therapy begins 1