At What Age Do Fontanelles Close? | Closure Timeline Facts

Most infants’ soft spots firm up on schedule: the back one by 1–2 months, the top one by 7–19 months, with a wide healthy range.

New parents hear “soft spot” and feel a jolt of worry. That’s normal. Fontanelles are meant to be there, and they change slowly, not overnight. Once you know the usual timing and what “off schedule” can mean, the whole topic gets a lot less scary.

This article lays out when each fontanel tends to close, what a clinician is feeling for during checkups, and which signs deserve same-day medical care.

What Fontanelles Are And Why Babies Have Them

Fontanelles are small gaps between skull bones. They’re covered by a tough membrane, not “open brain.” Those gaps let the skull shift during birth and give the brain room to grow during the first year. MedlinePlus explains how sutures and fontanelles stay flexible early on, then fuse as growth slows. MedlinePlus on cranial sutures gives the plain-language overview.

The Two Soft Spots Parents Notice Most

Babies can have more than two fontanelles, yet two get nearly all the attention:

• Posterior fontanelle: a small diamond-shaped area near the back of the head.
• Anterior fontanelle: a larger, softer area on the top of the head toward the front.

The back fontanelle is often tiny. Some babies have it closed at birth, and that can still be fine.

What “Closing” Means In Real Life

Closing is a gradual shift from soft-and-springy to firm-and-flat as bones meet and fuse. It is not a “snap shut” moment. You may still feel a slight give even after a clinician says it’s closing on time, since the edges can fuse unevenly.

At What Age Do Fontanelles Close In Most Babies

Two points help before you compare your baby to a chart. First, the back fontanelle closes early, often before you’ve had many pediatric visits. Second, the top fontanelle has a broad window, so a baby at 9 months and a baby at 16 months can both be within typical limits.

Posterior Fontanelle Closure Window

MedlinePlus notes that the posterior fontanelle usually closes by 1 to 2 months of age, and it may already be closed at birth. That same MedlinePlus page is a solid baseline when you want a conservative range.

Anterior Fontanelle Closure Window

The anterior fontanelle takes longer. MedlinePlus places closure “sometime within 7 to 19 months.” That span covers a lot of babies. In primary care, many clinicians talk about “around the first birthday,” with plenty of healthy kids outside that midpoint.

For a clinician-focused view, the American Academy of Family Physicians review of the abnormal fontanel reports a median closure time of 13.8 months, based on published studies. AAFP’s “The Abnormal Fontanel” also lists medical causes linked with a fontanel that is larger, bulging, or slow to close.

Why Timelines Vary From Baby To Baby

Skull growth is tied to brain growth, genetics, and overall growth tempo. A smaller baby may keep a small opening longer. A baby with a larger head may close later as well. That’s why clinicians pair the fontanel exam with head circumference trends across visits, not a single day on the calendar.

How Clinicians Check Fontanelles During Well Visits

At routine visits, a clinician is doing more than tapping the soft spot. They’re combining three checks:

1. Feel: soft and flat is the usual feel when the baby is calm and upright.
2. Size and edges: they note whether the opening is shrinking over time and whether the bony margins feel even.
3. Growth pattern: head circumference is plotted over time to match the baby’s own curve.

A short Mayo Clinic video shows the location of the soft spots and the basic idea of skull bones fusing. It’s useful if you want to match what you’re feeling with a clear visual. Mayo Clinic video on baby’s soft spots walks through that anatomy.

Clinicians also look for clues elsewhere: muscle tone, feeding, sleep, and overall development. A fontanel that seems “late” with steady growth and a thriving baby often leads to simple follow-up instead of tests.

What Timing Is Typical And What A Change Can Point To

Fontanelles are not a scorecard. They’re a small piece of a bigger picture. The table below puts the usual timing side-by-side with patterns clinicians often watch for, so you can see what tends to be routine and what tends to trigger a closer check.

Finding	Typical Age Or Context	What Clinicians Often Check
Posterior fontanelle no longer felt	Birth to 2 months	Head shape, head growth curve, birth history
Anterior fontanelle still open and soft	3 to 12 months	Head circumference trend, overall growth, exam findings
Anterior fontanelle closing gradually	7 to 19 months	Symmetry of bony edges, normal skull molding, growth tempo
Anterior fontanelle hard to feel early	First months	Head shape, suture ridging, family head-size pattern
Anterior fontanelle still open past toddler age	After 24 months	Growth curves, thyroid screening history, bone health clues
Bulging fontanelle when baby is calm and upright	Any age	Fever, irritability, neurologic signs, hydration status
Sunken fontanelle	Any age	Fluid intake, wet diapers, vomiting or diarrhea
Large fontanelle with slow growth or delayed milestones	Across multiple visits	Broader medical workup guided by exam and history

If a soft spot seems odd at home, a quick way to reduce false alarms is to check when your baby is upright and settled. Crying, straining, or lying flat can make the membrane look fuller for a short time.

Signs That Need Same-Day Medical Care

A fontanel can change with routine things like crying, yet some patterns deserve fast medical attention. Seek same-day care if any of these show up:

• A bulging soft spot paired with fever, repeated vomiting, unusual sleepiness, or a stiff neck.
• A bulging soft spot after a head injury.
• A sunken soft spot with fewer wet diapers, dry mouth, or ongoing vomiting or diarrhea.
• Seizure-like movements or a sudden change in alertness.

Children’s Hospital Colorado notes that a bulging or sunken fontanel can be a sign of a health issue, and it’s a common reason clinicians ask parents to call in. Children’s Hospital Colorado on fontanelles summarizes what “soft and flat” should feel like and flags bulging or sunken changes.

Reasons A Fontanel May Seem To Close Early Or Late

Timing shifts happen for many non-alarming reasons. A baby may simply follow a family pattern. A slightly earlier close can show up with a smaller fontanel size at birth. A slightly later close can track with a larger opening or a longer period of rapid head growth.

Early Closure Patterns Clinicians Watch For

When a fontanel seems to close early, clinicians often focus on head shape and head growth rate. A ridge along a suture or a head that grows too slowly can raise concern for early suture fusion. The fontanel alone is not the whole story; shape and growth carry a lot of weight.

Late Closure Patterns Clinicians Watch For

When the top fontanel stays open longer, clinicians often screen the basics first: nutrition, growth, and the head growth curve. In some cases they check for endocrine or bone issues. The AAFP review lists examples tied to delayed closure, such as hypothyroidism and rickets, along with genetic conditions and raised intracranial pressure. The AAFP article lays out those differential points in clinician language.

Fast Reference By Soft Spot

If you want a single place to anchor your expectations, this table keeps the two main fontanelles side-by-side. It’s not meant to replace a growth chart, yet it can help you decide whether what you’re feeling lines up with the usual windows.

Soft Spot	Usual Closure Window	What To Watch At Home
Posterior fontanelle (back)	Birth to 2 months	Head shape changes that seem sudden, paired with feeding or sleep changes
Anterior fontanelle (top/front)	7 to 19 months (many close near 12–18 months)	Bulging when calm, sunken with poor intake, head growth that shifts off its usual curve
Either fontanelle	Varies	New neurologic signs, fever with bulging, head injury with swelling

How To Feel A Soft Spot Safely

You can touch a fontanel gently. The membrane is tough, and routine handling during bathing, hair washing, and cuddling is safe. What helps is using a light, flat touch instead of poking with a fingertip.

Simple Steps That Make The Check Easier

1. Pick a calm moment, like after feeding.
2. Hold your baby upright against your chest.
3. Use the pads of two fingers to feel for a soft area, then the firmer bony edges.
4. Stop once you’ve located it. Re-checking again and again can ramp up worry without adding new info.

If you’re unsure you’re in the right spot, the Mayo Clinic visual can help you map the locations again. The Mayo Clinic clip is short and clear.

What To Track Between Appointments

You don’t need a daily ritual. A few notes can help you give a clean description at a visit:

• When you last felt the back fontanelle at all.
• Whether the top fontanelle feels flatter when your baby is upright and calm.
• Any pattern of bulging tied to fever.
• Feeding changes, vomiting, diarrhea, fewer wet diapers, or unusual sleepiness.

If you bring those notes, the clinician can pair them with the growth chart and the exam. That combo is usually what drives next steps.

Questions To Bring Up At A Checkup

If you want to use your visit time well, these question prompts tend to get you clear answers without turning the visit into a medical trivia session:

• “Does the fontanel feel right for my child’s age and head growth curve?”
• “Is the head shape and suture feel typical on exam?”
• “If you want a re-check, what timing makes sense?”
• “What signs should trigger a call the same day?”

Takeaway Checklist For A Calm Soft-Spot Read

Use this short checklist when you want a grounded check at home:

• Check when upright and calm, not mid-cry.
• Soft and flat is the usual feel.
• Back fontanelle often fades by 1–2 months.
• Top fontanelle often stays open through the first year and can close any time in the second year.
• Bulging with fever, vomiting, odd sleepiness, or after head injury needs same-day care.
• Sunken with poor intake and fewer wet diapers points to dehydration risk.

Most of the time, the story ends with reassurance and the next routine check. When something does need workup, early recognition helps your child get the right care fast.