Cranial Fontanelles in the Newborn

The skull is the skeletal structure of the head and is composed of 22 bones joined together by cranial sutures. In newborns, in addition to the bones and sutures, there are soft, fibrous areas known as cranial fontanelles, located at the junctions where two or more sutures meet.

The term fontanelle derives from the perception of a pulsation that may resemble the movement of water in a small fountain. These structures serve an essential function: they make the skull more flexible to facilitate passage through the birth canal and allow for the rapid growth of the brain, particularly during the first year of life.

Types and Characteristics of the Fontanelles

Overall, there are six fontanelles, but the two main and most easily palpable ones are:

• Anterior fontanelle (Bregma): diamond-shaped, measuring between 2 and 4 cm in diameter. It is the largest and most visible fontanelle.
• Posterior fontanelle (Lambda): triangular in shape, measuring approximately 1 cm in diameter.

Fontanelles are examined by palpation while the newborn is in a sitting position and in a calm state. Under these conditions, they feel like fibrous tissue overlying the cranial bones, and the pulsations that can be felt are entirely normal.

As the child grows, the fontanelles gradually close as fibrous tissue is replaced by bone:

• The posterior fontanelle closes between 6 weeks and 3 months of age.
• The anterior fontanelle begins to close around 6 months and completes closure between 18 and 24 months.

Fontanelle Abnormalities

• Sunken fontanelle: may indicate dehydration.

• Bulging or raised fontanelle: may occur during crying or when the baby is lying down.

Premature closure of the fontanelles (craniosynostosis) may interfere with normal skull growth, resulting in cranial deformities.

Prevention of Positional Plagiocephaly

Plagiocephaly (flattening of the skull) may develop when an infant spends prolonged periods lying on their back. To help prevent this condition, it is recommended to provide the baby with supervised tummy time, always under adult supervision. It is also advisable to alternate the baby’s head position in the crib or stroller, helping to prevent unilateral flattening caused by preferential visual or auditory stimulation.

Recommended Positioning

• Semi-reclined position: supports the trunk while allowing the head to move freely, encouraging exploration of the surrounding environment.
• Prone on the parent’s chest (0–2 months): promotes bonding and strengthens the neck and back muscles.
• Prone on the changing table (from 2 months onward): helps develop head control and the motor skills that prepare the child for crawling.
• Held in the arms: alternating the side on which the baby is carried promotes symmetrical neck muscle development and active head rotation.
• Held in a flexed (contained) position: maintain an ergonomic posture while alternating the side on which the baby is held.

The fontanelles are key structures in the newborn’s cranial development, and their proper observation provides valuable information about the infant’s overall health. At the same time, careful attention to positioning from the very first months of life is essential to promote harmonious development and help prevent positional cranial deformities.