Baby's Soft Spots (Fontanelles): What's Normal, When to Worry, and How to Care for Them

You touch the top of your baby's head and there is this soft dip that shifts under your fingers — and every instinct says leave it alone forever. That soft dip is a fontanelle, and it is one of the parts of a newborn most parents are quietly afraid of. It also isn't nearly as fragile as it feels.

Here is what the fontanelles actually are, when they close, what a healthy one looks like, and the specific changes — one sunken, one bulging — that mean call the doctor now. Every claim on this page traces to a pediatric hospital, MedlinePlus, or the American Academy of Pediatrics.

01What the soft spots actually are

A newborn's skull isn't one solid piece of bone. It is several plates that grow together over the first year and a half or so, and the gaps between them — "the diamond-shaped soft spots in between baby's skull plates that haven't yet joined together," as Cleveland Clinic describes them — are the fontanelles. Most babies have two you can feel: a bigger one on top of the head (the anterior fontanelle) and a smaller one lower down at the back (the posterior fontanelle), described by the American Academy of Pediatrics as "anterior for the larger one in the front, posterior for the smaller and typically less noticeable one in the back."

Those gaps are there for two very specific reasons. They let the skull bones shift and overlap so the head can squeeze through the birth canal, and — the bigger job — they leave room for the brain to keep growing fast during the first year. The AAP notes the fontanelles "will allow your baby's brain to grow rapidly throughout the next year."

They also feel a lot more fragile than they are. The AAP tells parents that even without a bony layer, the fontanelles "are well protected from typical day-to-day baby handling." Cleveland Clinic is more direct: "These soft spots are covered in skin and protected by a layer of tough membranes... even though they're called 'soft spots' they're still pretty hardy." Normal cuddling, feeding, dressing, hat-wearing, and gently washing over the head are all fine.

02When each soft spot closes

There are two, and they close on very different schedules.

The posterior fontanelle — the smaller one at the back — closes first. Cleveland Clinic says it is "about the size of a pencil eraser (0.5 cm in diameter)" and "typically closes by the time your baby is just 2 or 3 months old." Children's Hospital Colorado puts the posterior closure inside the first two months of life. Because it is small and tucked low on the head, many parents never really notice it at all.

The anterior fontanelle — the diamond-shaped one on top — is the one you will actually feel, and it stays open much longer. Cleveland Clinic puts it "about the size of a penny" at birth and says it "typically closes soon after your child's first birthday." Children's Hospital Colorado gives the wider normal range: "The anterior fontanelle closes between 7 and 18 months."

That range is wide on purpose. Some perfectly healthy babies close up on the earlier side, others closer to a year and a half. Children's Hospital Colorado's plain rule: "If you feel your baby's fontanelles are closing too soon or haven't closed in 18 months, consult your pediatrician."

03What a healthy soft spot actually feels like

You do not have to guess whether the soft spot looks right — there is a normal, and it is specific.

A healthy fontanelle sits flat, or dips inward just very slightly, and feels firm rather than mushy. MedlinePlus describes the baseline this way: fontanelles "should feel firm and very slightly curved inward to the touch." Cleveland Clinic says the top of the head should be "mostly flush with the rest of their" head.

Two things that look alarming and aren't:

• A gentle pulse. The AAP notes that "the soft spot on the top of your baby's head may seem to be pulsating. There is no need to worry — this movement is quite normal and simply reflects the visible pulsing of blood that corresponds to your baby's heartbeat."
• A brief rise when your baby cries, coughs, or lies down. MedlinePlus is explicit: "When the infant is crying, lying down, or vomiting, the fontanelles may look like they are bulging. However, they should return to normal when the infant is in a calm, head-up position."

Both are normal. The signs that aren't come next.

04The sunken soft spot — a dehydration sign

A soft spot that curves in noticeably — visibly dipped, not just very slightly flat — is a sign a baby doesn't have enough fluid on board. MedlinePlus calls a sunken fontanelle "an obvious curving inward of the 'soft spot' in an infant's head" and points to dehydration as the main cause: "not enough fluid in the body."

The AAP describes the pattern to look for: "In young infants, a sunken soft spot (when combined with poor feeding and dry diapers) can suggest dehydration." Cleveland Clinic lists the other dehydration cues you will usually see alongside it — fewer wet diapers than usual, a dry mouth or lips, extra sleepiness or fussiness, and few or no tears when crying.

• If it looks slightly sunken and your baby is otherwise okay, Cleveland Clinic's first move is to offer more feeds: "Encourage your baby to drink more by offering extra bottles or breastfeeding sessions." Then call your pediatrician if the sunken look "persists and you can't get your baby to take in more fluids."
• If it looks obviously sunken, or your baby also has vomiting, diarrhea, a hot room, or seems limp or hard to wake, treat it urgently. MedlinePlus is direct: "A sunken fontanelle can be a medical emergency. A health care provider should check the infant right away."

05The bulging soft spot — pressure inside the skull

The other direction — a soft spot that bulges outward when your baby is calm and upright — is the more urgent of the two. MedlinePlus explains why: "A tense or bulging fontanelle occurs when fluid builds up in the brain or the brain swells, causing increased pressure inside the skull."

That pressure has several possible causes, all of which need a doctor to sort out. MedlinePlus names infections that can inflame the brain or its lining — "encephalitis" ("swelling (inflammation) of the brain, most often due to infections") and "meningitis" ("infection of the membranes covering the brain") — plus "hydrocephalus," "a buildup of fluid inside the skull." Cleveland Clinic adds that after a fall, "a swollen soft spot is sometimes a sign of head trauma. It may also be accompanied by vomiting."

Do not wait on this one. MedlinePlus's rule: "Immediate, emergency care is needed for any infant who has a truly bulging fontanelle, especially if it occurs along with fever or excess drowsiness." Cleveland Clinic says the emergency signs to watch for alongside the bulge are "fatigue, vomiting or changes in your baby's temperament — like if they're extra sleepy or fussy."

06The easy part — how to wash and touch it

Because parents are so cautious with the fontanelle, the top of the head is often the part that never really gets cleaned — and that is exactly where cradle cap builds up. It is fine, and useful, to wash gently over the soft spot as part of a regular bath.

The AAP's reassurance is worth repeating: fontanelles "are well protected from typical day-to-day baby handling." A soft cloth or a soft baby brush over the whole scalp is fine. If flaky, greasy patches are already there, our cradle-cap guide walks through the gentle brushing routine pediatricians actually recommend. Bathing itself only needs to happen a few times a week in the newborn phase — the newborn bath basics piece covers frequency and setup.

07If a soft spot closes too early — or too late

Two edges of normal are worth naming so you know what a pediatrician is checking for.

Closes too early. If the skull plates knit together before the brain is done growing, the head can't expand the way it needs to. Cleveland Clinic describes this as "craniosynostosis": "occasionally, the skull bones do close earlier than normal on one side. That causes a condition called craniosynostosis." It can lead to an unusual head shape — "sagittal craniosynostosis, the most common form, results in a longer head that is shaped somewhat like a football" — and is treated with a shaping helmet or, in some cases, surgery. Children's Hospital Colorado adds that early closure of the anterior fontanelle "can limit brain growth or create an abnormal head shape."

Closes too late. A soft spot that stays open past 18 months, especially one that stays large, is not automatically a problem — but it is a reason to talk to the pediatrician. Cleveland Clinic lists conditions that are sometimes linked to a late-closing fontanelle: "Down syndrome, Achondroplasia, Congenital hypothyroidism, Rickets, [or] Abnormally high amounts of pressure in the brain." The same page adds the sensible caveat: "These conditions come with other symptoms. No need to prematurely rush to conclusions if your baby is otherwise developing normally."

Both edges are things your pediatrician is already watching for. Cleveland Clinic: "Checking baby's fontanelle is a regular part of visits with a pediatric healthcare provider, like during well-child checkups. Your baby's provider may measure their head and lightly feel their fontanelles as part of their standard exam."

08One less part to be afraid of

The soft spot ends up being one of the parts of a newborn that reads scarier than it is. Flat, firm, gently pulsing — normal. Sunken with dry diapers — feed and call. Bulging while calm, or with a fever, or after a fall — go now. Everything else you can hand to a burp cloth and a soft brush. The rest of the newborn learning curve is on our newborn basics guide, and if you are still pregnant, our free week-by-week planner puts the parts of the early weeks worth reading up on in front of you before they arrive.

Questions parents actually ask

Newborn Weeks is planning help, not medical advice — always follow your own doctor, midwife, or pediatrician.