Fontanelles are the soft, membrane-covered gaps between a newborn’s cranial bones, the places where the skull plates have not yet fused. The familiar “soft spot” near the top of a baby’s head is one of those gaps, and it exists so the skull can squeeze through the birth canal and then make room for a brain that roughly doubles in size during the first year. Knowing what those gaps are, where they sit, and how they change over time turns a nerve-wracking feature into something you can handle with confidence.
This guide walks new parents through every aspect of fontanelles, from the anatomy behind those soft skull gaps to when each one typically closes, so you can care for your baby with confidence.
The Soft Spots Every Newborn Is Born With
A newborn skull is built from several bone plates that meet along fibrous seams called sutures, and at the corners of those seams sit the fontanelles. These gaps are filled with a tough, flexible membrane rather than bone, which is why they feel slightly spongy under a fingertip and may pulse with the heartbeat underneath. The membrane handles normal caregiving easily, despite the delicate reputation that has grown up around it.
Most babies are born with six fontanelles in total, though only two of them are easy to feel without clinical training:
- Anterior fontanelle: the largest, sitting at the top of the head where the forehead meets the crown. It often looks like a diamond-shaped dip and may visibly throb with each heartbeat.
- Posterior fontanelle: smaller and triangular, located toward the back of the skull just above the nape of the neck.
- Two sphenoid fontanelles: paired points on the sides of the skull near the temples, generally too small to feel without clinical practice.
- Two mastoid fontanelles: paired points behind each ear, again too subtle for most parents to detect by touch alone.
The reason most caregiving guides focus on the anterior and posterior fontanelles is straightforward: those are the ones you can actually find with your fingers during everyday moments. Recognizing them in the first few weeks of life gives you an easy mental map of where the skull is still open and where it has already knit together.
Why Babies Arrive With Gaps in Their Skull
During a vaginal birth, the skull bones actually overlap and slide against each other as the head passes through the birth canal. The medical term for this temporary reshaping is molding, and it can leave a newborn’s head looking slightly pointed or uneven for the first day or two. Without those flexible seams and membrane-filled gaps, that compression could not happen safely.
Once your baby is born, the same flexible design lets the cranial vault expand rapidly. The brain grows faster in the first year than at any other point in life, and the skull has to grow with it. it also act as a small built-in pressure relief, giving the skull extra room to absorb mild bumps or short-lived swelling without injuring the brain underneath.
Think of the soft spot less as a weakness and more as a hinge. It lets the skull flex during birth, expand during growth, and absorb minor everyday knocks.
That mental shift matters because it changes how you approach handling. The membrane is not a thin sheet of glass that can shatter under a finger; it is a tough, slightly elastic layer that exists precisely to protect the brain while the skull is still under construction.
That protective stretch only matters if you can locate each soft spot, and they sit in surprisingly specific places.
Where Each Fontanelle Sits and How It Feels
Finding the anterior fontanelle is easy once you know where to look. Run your finger up the centerline of the forehead until you reach the soft area where a headband would sit, near the crown of the head. Under normal conditions, the spot feels slightly concave, gives a little under gentle pressure, and may pulse in time with your baby’s heartbeat. That pulse is just the underlying artery, and seeing it move is a reassuring sign, not a warning.
The posterior fontanelle sits much lower, at the upper back of the skull just above the nape of the neck. It feels like a small, shallow triangle and is often barely detectable once a baby is past the newborn stage. Because it closes earlier, you may notice it disappearing within the first few months.
What a Normal Fontanelle Looks and Feels
A healthy fontanelle is firm but yielding, much like a taut drum skin. When your baby is calm and upright, a slight inward curve is normal. When your baby is crying, straining, or lying down, a mild outward bulge is also normal because the pressure inside the skull briefly rises.
Good moments to learn the feel of both it are after a feed, during a calm diaper change, or while your baby is being burped and is already relaxed. Practice during these quiet windows, and you will quickly build a baseline for what is normal for your own child.
What an Abnormal Fontanelle Looks and Feels
A truly sunken or deeply hollowed spot when your baby is calm, especially alongside fewer wet diapers or a dry mouth, is a classic sign of dehydration. A bulging spot when your baby is calm, paired with fever, vomiting, or unusual sleepiness, points toward increased pressure inside the skull and warrants immediate medical attention. A fontanelle that feels rock-hard or persistently tense, rather than just briefly firm during crying, also falls outside the normal range.
Handling, Bathing, and Holding Without Worry
Normal caregiving poses no risk to the membrane. Gentle washing with a soft, damp cloth over the fontanelle is safe and recommended, even during the first sponge bath. There is no need to scrub, press hard, or avoid the area; ordinary care is exactly what the membrane is built to tolerate.
Supporting the head during burping, cuddling, and sleep positioning protects the soft spots naturally, and standard newborn head support is all that is required. Hair washing, baby oil massages, and light kisses on the scalp also pose no risk. Pediatric guidance from the American Academy of Pediatrics treats it as routine contact areas during daily care.
Everyday Scenarios That Are Safe
- Washing the scalp: a soft cloth with warm water is enough; no need to avoid the spot.
- Burping and holding: standard head support across the back of the neck is all the protection needed.
- Kissing or stroking the top of the head: harmless, regardless of how often it happens.
- Light baby oil or lotion massage: fine on the scalp, including over the anterior fontanelle.
Items Worth Discussing With Your Pediatrician
Reflux wedges, specialty pillows, and helmets for positional plagiocephaly (flat head syndrome) are not automatically off-limits, but they are worth flagging at a well-baby visit. Your pediatrician can confirm that any device you use is properly fitted and appropriate for your baby’s age and head shape.
After a Minor Bump
A small, temporary bump on the soft spot from rolling into a coffee table or a sibling’s elbow is usually harmless. Watch the area for about an hour. A small raised patch that fades, with no change in behavior, is reassuring. Persistent swelling, bruising that spreads, vomiting, or unusual sleepiness after any head bump is a reason to call your pediatrician right away.
Once you know how to find and feel them, the next concern parents usually raise is whether everyday handling can actually injure those gaps.
Closure Timing and What Early or Late Closure Means
The posterior fontanelle is the early one. It typically closes within the first two to three months of life and is rarely felt past the fourth month. The anterior fontanelle, being larger, takes much longer. Most pediatric resources place normal closure somewhere between 18 and 24 months, with healthy closure seen as early as 9 months and as late as 27 months in some children.
How Pediatricians Track Closure
At every well-baby visit, your pediatrician gently feels the soft spot and measures head circumference. Those two checks, combined with the appearance of the skull sutures, give a complete picture of how the cranial vault is developing. Tracking closure is therefore a routine pediatric observation, not something you need to monitor obsessively at home.
| Fontanelle | Typical Closure Window | What Persistent Openness May Signal |
|---|---|---|
| Posterior | 2–3 months | Rare; sometimes linked to thyroid or bone conditions when persistently open |
| Anterior | 18–24 months (range 9–27 months) | Delayed closure can reflect thyroid, growth, or skeletal concerns |
| Shenoid and mastoid | Usually within 6–18 months | Seldom relevant unless paired with other findings |
Early Closure (Craniosynostosis)
Premature fusion of one or more skull sutures, called craniosynostosis, can restrict brain growth and reshape the skull. It is usually picked up at well-baby visits through an oddly shaped head or a closed fontanelle earlier than expected. When caught early, surgical correction is often straightforward, and outcomes for healthy brain development are excellent.
Late Closure
A fontanelle that stays open past the upper end of the normal range can sometimes point toward thyroid conditions, certain bone disorders, or generalized growth concerns. This is one reason pediatricians check the spot at every visit. Treating closure timing as data for your pediatrician, rather than a self-diagnosis, keeps worry in proportion.
Most soft spots close on a predictable schedule, and knowing that range helps you spot when something falls outside it.
Normal Variations Versus Signs That Need a Doctor
Most of what you see at the soft spots is normal. Mild bulging while crying, a faint pulse at rest, and a gentle inward curve when calm are all everyday findings. The table below can serve as a quick reference during those uncertain 2 a.m. moments.
| Observation | Likely Normal | Call the Pediatrician |
|---|---|---|
| Slight bulge while crying or straining | Yes | Only if it stays bulging when calm |
| Visible pulse | Yes | No concern on its own |
| Mild inward curve when calm and upright | Yes | Only if deeply sunken or paired with dehydration signs |
| Bulging with fever, vomiting, or lethargy | No | Urgent evaluation needed |
| Sunken with fewer wet diapers, dry lips | No | Same-day medical contact |
| Rock-hard or persistently tense | No | Prompt evaluation |
Common Myths Worth Letting Go
- “Never touch the soft spot.” Touching during normal care is safe and is in fact how parents learn what is normal for their own baby.
- “Heavy oils will close it faster.” No topical remedy closes a fontanelle; closure happens on its own biological timeline.
- “A small fontanelle means a smarter baby.” Size has no link to intelligence, and a smaller-than-average spot is usually just normal variation.
A Simple At-Home Routine
A weekly check during normal cuddling is plenty. While your baby is relaxed, gently feel for the anterior fontanelle’s contour, note whether it looks sunken or bulging when calm, and watch for energy, feeding, and wet-diaper patterns over the day. If anything feels off compared to the baseline you have built, that is your cue to call the pediatrician.
The Bottom Line
it are not vulnerabilities to be tiptoed around; they are deliberate, protective gaps that let a baby’s skull handle birth and rapid brain growth. Most of what you will see and feel is normal, and the small handful of signs that are not normal (bulging when calm, sunken with dehydration cues, persistently tense, or a head shape that looks off) are exactly what your pediatrician screens for at every visit. Hold, wash, and cuddle your baby without worry, and let the routine well-baby checks do the heavy lifting on closure and growth.
FAQ
What are fontanelles and why do babies have them?
it are the soft, membrane-covered gaps between the skull bones of a newborn. They let the skull compress safely during birth and expand as the brain grows rapidly during the first year of life.
How many fontanelles does a newborn have?
Most newborns have six it: one anterior, one posterior, two sphenoid, and two mastoid. Parents typically only feel the anterior and posterior ones during everyday care.
When do the soft spots on a baby’s head close?
The posterior fontanelle usually closes within 2 to 3 months, while the anterior fontanelle commonly closes between 18 and 24 months, with healthy variation from about 9 to 27 months.
What does a bulging fontanelle indicate?
A fontanelle that bulges when the baby is calm, especially with fever, vomiting, or unusual sleepiness, can signal increased pressure in the skull from conditions such as meningitis, encephalitis, or hydrocephalus and warrants urgent medical evaluation.
Is it normal for a fontanelle to pulsate?
Yes. A visible or felt pulse reflects the underlying artery and is a normal finding, particularly over the anterior fontanelle.
When should I be concerned about my baby’s soft spot?
Call your pediatrician if the soft spot bulges when calm, feels rock-hard, or looks deeply sunken alongside signs of dehydration such as fewer wet diapers, dry lips, or lethargy. Any major head bump followed by vomiting, persistent swelling, or behavior change also needs same-day attention.
