Fontanelles, commonly known as “soft spots,” are gaps between the bones of an infant’s skull where the bones have not yet fused together. These membranous areas play a crucial role in childbirth and early brain development, serving as one of nature’s most ingenious designs for human infants.
What Are Fontanelles?
Fontanelles are soft, membrane-covered spaces between the cranial bones of a newborn’s skull. Unlike the solid, fused skull of an adult, a baby’s skull consists of several separate bony plates connected by flexible fibrous tissue called sutures. Where multiple sutures meet, larger gaps form—these are the fontanelles.
The skull doesn’t develop as a single piece of bone. Instead, it grows from multiple ossification centers that gradually expand and eventually fuse. This process, called cranial ossification, continues well into childhood.
Types and Locations
A newborn typically has six fontanelles, though two are most prominent and clinically significant:
The Anterior Fontanelle is the largest and most well-known soft spot. Located at the top front of the head where the frontal and parietal bones meet, it’s diamond-shaped and measures approximately 2-3 centimeters across at birth. This fontanelle usually closes between 12 and 18 months of age, though closure anywhere between 7 and 19 months is considered normal.
The Posterior Fontanelle sits at the back of the head where the parietal and occipital bones converge. Triangular in shape and much smaller than its anterior counterpart, it typically measures about 0.5-1 centimeter and usually closes by 2-3 months after birth.
The Sphenoid Fontanelles (two, one on each side) are located at the temples, where the frontal, parietal, temporal, and sphenoid bones meet. These close around 3 months of age.
The Mastoid Fontanelles (two, one on each side) are positioned behind the ears where the parietal, occipital, and temporal bones converge. These also typically close around 3 months of age.
Why Do Fontanelles Exist?
Fontanelles serve several vital functions:
Facilitating Childbirth: Perhaps their most important role, fontanelles allow the baby’s skull to compress and mold during passage through the birth canal. The overlapping of skull bones, called molding, enables the relatively large infant head to navigate the confined space of the pelvis. Without this flexibility, vaginal delivery would be nearly impossible for humans.
Accommodating Rapid Brain Growth: The human brain grows dramatically during the first year of life, nearly doubling in size. Fontanelles and unfused sutures allow the skull to expand to accommodate this rapid growth without restricting brain development. A prematurely fused skull could constrain brain growth and lead to serious complications.
Allowing for Head Growth: Beyond just brain expansion, the overall size of the head increases substantially during infancy. The flexible skull structure permits proportional growth.
Normal Appearance and What to Expect
Understanding what’s normal can help parents feel more comfortable caring for their infant:
A healthy fontanelle should appear flat or slightly depressed when the baby is calm and upright. It’s normal to see slight pulsations in the anterior fontanelle, reflecting the baby’s heartbeat and blood flow—this is not a cause for concern.
The fontanelles are covered by a tough, protective membrane and a layer of skin, making them more resilient than many parents realize. Normal, gentle touching during hair washing, combing, or examination won’t harm the baby.
Warning Signs: When to Seek Medical Attention
While fontanelles are normal features of infant anatomy, changes in their appearance can sometimes indicate health problems:
A Sunken or Depressed Fontanelle may indicate dehydration, especially if accompanied by other signs like decreased urination, dry mouth, lethargy, or sunken eyes. This requires prompt medical evaluation.
A Bulging Fontanelle when the baby is upright and calm could signal increased intracranial pressure from conditions such as meningitis, encephalitis, hydrocephalus, or brain hemorrhage. If accompanied by fever, vomiting, lethargy, irritability, or seizures, this is a medical emergency.
Early Closure (craniosynostosis) occurs when fontanelles or sutures fuse prematurely, potentially restricting brain growth and causing skull deformities. This requires evaluation by a pediatric specialist and may need surgical intervention.
Delayed Closure beyond the normal timeframe might indicate underlying conditions such as hypothyroidism, rickets, Down syndrome, or other developmental disorders, and should be evaluated by a pediatrician.
Caring for Baby’s Fontanelles
Parents can follow these simple guidelines:
- Handle with confidence but care—normal gentle touching is safe
- Keep the area clean during regular bathing
- Protect the head from direct trauma or injury
- Use appropriate headwear in extreme weather
- Avoid applying excessive pressure to the soft spots
- Watch for concerning changes in appearance
Cultural Beliefs and Misconceptions
Various cultures hold different beliefs about fontanelles, some viewing them with special reverence or concern. While respecting cultural perspectives, it’s important to distinguish traditional beliefs from medical facts. The soft spots are a normal part of infant development, not areas of vulnerability to spiritual harm or magical influence.
Some parents worry excessively about touching the fontanelles, but normal caregiving activities like washing hair, gentle combing, or touching the baby’s head won’t cause harm. The protective membrane is quite tough.
Conclusion
Fontanelles represent an elegant evolutionary solution to the challenge of birthing large-brained human infants while allowing for continued rapid brain growth after birth. These temporary gaps in the skull, far from being weaknesses, are essential features that enable both safe delivery and healthy development.
Understanding fontanelles—their purpose, normal appearance, and warning signs—empowers parents to care for their infants confidently while remaining appropriately vigilant for potential problems. As with many aspects of infant care, knowledge replaces anxiety, allowing parents to marvel at the remarkable design of human development rather than worry unnecessarily about these perfectly normal soft spots.
