A baby’s skull looks noticeably different from an adult’s. Instead of one solid, fused structure, it’s made up of several separate bone plates connected by flexible tissue, with visible soft spots where bones haven’t yet met. The overall shape is rounder and top-heavy compared to an adult skull, with a proportionally much larger braincase and a small, tucked-under face. Right after birth, the skull may also look temporarily misshapen from the delivery process.
Separate Bones Instead of a Single Shell
An adult skull feels like one continuous piece of bone, but a newborn’s skull is actually a puzzle of individual plates. Two frontal bones form the forehead, two large parietal bones cover the top and sides, and the occipital bone forms the back. These plates are connected by seams of fibrous tissue called sutures, which run between each bone and allow the skull to flex.
The major sutures include the sagittal suture (running front to back between the two parietal bones), the coronal sutures (running from ear to ear between the frontal and parietal bones), the metopic suture (between the two frontal bones), and the lambdoid sutures (between the parietal bones and the occipital bone at the back). These seams stay open throughout infancy and early childhood so the skull can expand as the brain grows. New bone forms along each suture’s edges, and the skull grows outward in the direction perpendicular to each seam.
The Soft Spots
Where several sutures meet, there are gaps covered only by a tough membrane rather than bone. These are the fontanelles, commonly called soft spots. A newborn has six of them, but two are large enough to feel easily.
The anterior fontanelle sits on top of the head, toward the front, where the two frontal bones and two parietal bones converge. It’s diamond-shaped and averages about 2.1 cm across, though it can range from 0.6 to 3.6 cm. This is the soft spot most parents notice. It doesn’t fully close until around 12 to 18 months of age.
The posterior fontanelle is at the back of the head, where the parietal bones meet the occipital bone. It’s smaller (roughly 0.5 to 0.7 cm), triangular, and closes much sooner, typically within six to eight weeks after birth. The remaining four fontanelles are small and located on the sides of the skull.
You may notice a gentle pulsing at the anterior fontanelle. This is normal and simply reflects the baby’s heartbeat through the blood vessels running beneath the membrane. The membrane covering a fontanelle is strong connective tissue, not just skin. Gentle touching during bathing or daily care won’t harm it.
Why Newborns Often Have Cone-Shaped Heads
Because the skull bones aren’t fused, they can shift and overlap during a vaginal delivery. This is called molding, and it’s one of the first things parents notice. The head may look elongated, lopsided, or even cone-shaped right after birth. This is completely normal and typically resolves within days.
Some of that cone shape comes from swelling of the scalp’s soft tissue during delivery, which usually fades within about six days. Babies born breech often have a distinctly long, narrow head shape with a prominent bump at the back of the skull, resulting from their in-utero positioning. In all these cases, the skull gradually rounds out on its own.
In the weeks after birth, a baby who consistently sleeps with their head turned to one side may develop a flat spot on that side of the back of the skull. When this happens, the head can take on a parallelogram shape: one side of the back flattens while the opposite side of the forehead becomes more prominent. This positional flattening is common and usually improves as the baby starts moving their head more freely.
Proportions That Look Different From an Adult
A baby’s head is proportionally much larger relative to the body than an adult’s. The braincase (the upper dome that houses the brain) dominates the skull, while the face is small and set low, almost tucked beneath the forehead. Babies have prominent foreheads and rounded sides because the frontal and parietal bones bulge outward to accommodate a brain that’s already a significant fraction of its adult size at birth. The facial bones, jaw, and sinuses are underdeveloped and won’t reach adult proportions until the teenage years.
What the Soft Spots Can Tell You
The fontanelles act as a visible window into a baby’s hydration and brain health. A fontanelle that looks noticeably sunken or concave often signals dehydration, particularly if the baby has been sick, vomiting, or not feeding well. On the other hand, a fontanelle that looks swollen or bulging outward can indicate increased pressure inside the skull. This can be caused by a viral or bacterial infection, or in rarer cases, a condition called hydrocephalus, where fluid builds up around the brain.
A fontanelle that appears slightly concave when the baby is upright and flat when the baby is lying down is normal. The key warning signs are persistent bulging (especially when the baby is calm and upright) or a noticeably sunken appearance paired with signs of illness.
When Sutures Close Too Early
In a small number of babies, one or more sutures fuse prematurely, a condition called craniosynostosis. Because the brain continues to grow, it pushes outward through whichever sutures remain open, creating a distinctly abnormal head shape that depends on which suture closed.
If the sagittal suture (the one running front to back along the top) closes early, the head grows long and narrow. If one of the coronal sutures (running from ear to ear) closes early, the forehead flattens on the affected side and bulges on the other, with the nose and eye socket shifting as well. If both coronal sutures close, the head becomes short and wide with the forehead tilting forward.
Unlike positional flattening, craniosynostosis doesn’t improve with repositioning. The skull shape becomes more pronounced over time rather than resolving. It’s typically identified within the first few months of life, and treatment involves surgery to reopen the fused suture and allow the brain room to grow normally.