The soft spot on top of a baby’s head, called the anterior fontanelle, typically closes between 13 and 16 months of age, though there’s a wide range of normal. Some babies’ soft spots close as early as three months, while others stay open until close to 24 months. The smaller soft spot at the back of the head usually closes by one to two months old, and it may already be closed at birth.
Why Babies Have Soft Spots
A newborn’s skull isn’t one solid piece of bone. It’s made up of several smaller plates connected by flexible, fibrous joints called sutures. The gaps where multiple sutures meet form the soft spots, or fontanelles. This design serves two purposes: it allows the skull bones to shift and overlap during delivery, which is why many newborns have slightly cone-shaped heads, and it gives the brain room to grow rapidly during the first two years of life.
Closure Timeline by Location
Babies actually have more than one soft spot, though most parents only notice the large diamond-shaped one on top of the head.
- Posterior fontanelle (back of head): Closes by 1 to 2 months. Often already closed at birth.
- Anterior fontanelle (top of head): Closes between 13 and 16 months on average, with a normal range extending up to about 24 months.
The anterior fontanelle is the one parents feel when they touch the top of their baby’s head. At birth, it measures roughly 4 centimeters front to back and 2.5 centimeters across, though size varies significantly between populations and individual babies. Your pediatrician will check the fontanelle at each wellness visit, feeling its size, shape, and tension as one indicator of healthy development.
What Affects Closure Timing
There’s no single “right” age for the soft spot to close. Ethnicity and sex both influence the timeline, and studies have found healthy children whose fontanelles closed anywhere from a few weeks old to well past their first birthday. One large study of healthy Brazilian children found a 40% closure rate by a mean age of about 10 months, showing just how much variation exists even within a single population.
Because of this natural variability, pediatricians look at the overall pattern of your baby’s growth and head circumference rather than treating fontanelle closure as a pass-fail milestone. A soft spot that’s still open at 14 months in an otherwise healthy baby is not a concern.
What’s Normal to See and Feel
The soft spot can look and feel different depending on what your baby is doing. When your baby is calm and upright, you might notice a slight pulsing in the fontanelle. This looks alarming but is completely normal. The pulsations match your baby’s heartbeat and reflect blood flowing through the vessels near the surface of the brain. You may also notice the fontanelle looks slightly flatter when your baby is lying down and slightly more concave when sitting up.
Gentle everyday contact with the soft spot, like washing your baby’s hair or brushing over it, won’t hurt your baby. The fontanelle is covered by a tough membrane that protects the brain underneath. You don’t need to avoid touching it.
Signs the Soft Spot Closed Too Early
When one or more of the joints between skull bones close before the brain has finished growing, it’s called craniosynostosis. This condition is present at birth and causes the skull to develop an unusual shape because the brain continues to expand in whichever direction still has open sutures.
The signs are usually visible at birth or become clearer in the first few months. They include a head shape that looks asymmetrical or unusually narrow, wide, or pointed, depending on which suture closed. You might notice a hard ridge along the skull where you’d expect to feel a flexible seam, or that your baby’s facial features seem uneven, with one eye or ear sitting higher than the other. In more severe cases involving multiple sutures, symptoms can include headaches and seizures.
Not every unusual head shape means craniosynostosis. Positional flattening from sleeping in one position is far more common. But if you notice a hard ridge or progressively unusual head shape, your pediatrician can evaluate whether the sutures are closing as expected.
Signs the Soft Spot Is Still Open Too Long
A fontanelle that remains large and open well past 24 months can sometimes signal an underlying condition. Rickets (from vitamin D deficiency), certain thyroid conditions, and some genetic syndromes are among the possible causes. In practice, this is something your pediatrician tracks over multiple visits rather than something you’d need to spot at home, since fontanelle size shrinks gradually and the change can be hard to judge by touch alone.
When the Soft Spot Itself Looks Wrong
Two changes in the fontanelle’s appearance can signal a problem that needs prompt attention.
A noticeably sunken soft spot is often a sign of dehydration. You’re most likely to see it when your baby has been sick with vomiting or diarrhea and hasn’t been taking in enough fluids. Other signs to look for include fewer wet diapers than usual, dry mouth or lips, few or no tears when crying, and unusual sleepiness or fussiness.
A bulging fontanelle, one that looks swollen or feels tense and firm when your baby is calm and upright, can indicate increased pressure inside the skull. This can result from infections like meningitis, bleeding in the brain, or a buildup of fluid around the brain. A bulging fontanelle, especially with fever, vomiting, or extreme irritability, needs immediate medical evaluation.
It’s worth noting that the fontanelle can temporarily bulge when a baby is crying hard or straining. The key distinction is whether it stays raised when the baby is calm and in an upright position.