At what age do a baby's fontanelles (soft spots) typically close?

When Do Babies' Fontanelles Close?

The anterior fontanelle typically closes at a median time of 13.8 months, with normal closure occurring between 6.6 and 22.4 months of age. 1, 2

Anterior Fontanelle Development and Closure

• The anterior fontanelle is the largest of six fontanelles present at birth and the most important for clinical evaluation 1
• The average size of the anterior fontanelle at birth is approximately 2.0-2.1 cm 1, 2
• Fontanelle size gradually decreases with age:
  • 2.0 cm at 1 month of age 2
  • 0.6 cm by 12-14 months 2
  • Complete closure typically by 21-23 months 2

Timing of Fontanelle Closure

• The mean age for anterior fontanelle closure is 14.5 months (95% CI 14.4-14.6 months) 2
• The normal range for closure (3rd to 97th percentile) is between 6.6 and 22.4 months 2
• By 15-17 months of age, approximately 67.5% of children have closed anterior fontanelles 2
• Girls tend to have slightly later closure times (10.3 ± 4.7 months) compared to boys (9.2 ± 5.1 months) 3

Factors Affecting Fontanelle Closure

• Physical development correlates with fontanelle closure:
  • Children with closed fontanelles typically have significantly higher height and weight measurements than those with open fontanelles at the same age 2
  • However, head circumference does not show significant correlation with fontanelle closure 2
• Early fontanelle closure is not necessarily associated with microcephaly 3

Clinical Significance of Abnormal Fontanelles

• A persistently large anterior fontanelle or delayed closure may indicate:
  • Achondroplasia
  • Hypothyroidism
  • Down syndrome
  • Increased intracranial pressure
  • Rickets 1
• A bulging fontanelle may suggest increased intracranial pressure or intracranial/extracranial tumors 1
• A sunken fontanelle often indicates dehydration 1
• It's important to note that some healthy children may have fontanelles that remain open beyond the typical closure time without any underlying pathology 4

Measurement Techniques

• Both traditional and oblique measurement techniques are equally accurate for assessing fontanelle size 3
• Children with fontanelles measuring above the 95th percentile should be monitored closely and potentially investigated for associated conditions 3