Baby's Soft Spot: Fontanelles

What are Fontanelles?

Fontanelles are the membrane-covered gaps on babies' heads where bones have yet to fuse together. When your baby's skeleton starts developing, multiple bony plates make up her skull. Over time, these bones will join together into a hard shell completely surrounding her brain.

Until then, you'll likely notice the soft spot on the top of the head called the . It’s not the only one. Babies have another soft spot, called the posterior fontanelle, toward the back of their heads. This gap is smaller and it closes up much earlier.

Anterior Fontanelle:

Location:
The anterior fontanelle is situated on the top of a baby's head, towards the front. It's where the two parietal bones and the two frontal bones of the skull meet.

Shape:
It's typically diamond-shaped.

Characteristics:
This is the larger of the two fontanelles, and you can often feel a gentle pulsation here.
It generally closes between 12 and 18 months of age.

Posterior Fontanelle:

Location:

The posterior fontanelle is located on the back of the baby's head.

Shape:

It's usually triangular in shape.

Characteristics:

This fontanelle is much smaller than the anterior fontanelle.
It typically closes much earlier, often between 2 and 3 months of age, and sometimes it's already closed at birth.

The soft spots on your baby’s head may look and feel fragile, but the good news is that they’re well-protected thanks to that sturdy membrane covering them. That means it’s okay to touch them gently. In fact, you won’t be able to avoid coming into contact with your baby’s fontanelles as you go about your routine, whether it's when you delicately shampoo her hair or steady her wobbly head with your hand.

Other Smaller Fontanelles:

While the anterior and posterior fontanelles are the most well-known, newborns actually have six fontanelles in total. The other four (two sphenoid and two mastoid fontanelles) are much smaller and tend to close very quickly after birth.

To be more precise, the infant's 6 cranial fontanelles close:

• Around II-III months of life, for the posterior fontanelle;
• Around the 18th month of life, for the anterior fontanelle;
• Around the sixth month of life, for the sphenoid fontanelle;
• Between the 6th and 18th month of life, the mastoid fontanelle.

Why do babies have soft spots?

Though it may seem as if your baby’s soft spots were put there to make you anxious, they actually play an important role. The fontanelles give a baby’s head the flexibility it needs to squeeze through the narrow birth canal — which is why a newborn can look pointy-headed for a little while after a vaginal birth.
After birth, they stay open long enough to accommodate your baby’s rapidly growing brain. In fact, one way your baby’s pediatrician will check your baby’s growth and development is by gently feeling her soft spots.

Secondly, fontanels are crucial for the rapid brain growth that occurs during infancy. The first year of life is marked by an extraordinary increase in brain size, and the unfused skull plates, connected by the fontanels, provide the necessary space for this expansion. As the brain grows, the skull gradually expands to accommodate it. The fontanels act like expansion joints, allowing for this dynamic growth without putting undue pressure on the developing brain.

Furthermore, fontanels offer medical professionals valuable insights into a baby's health. By gently palpating the fontanels, doctors can assess the baby's hydration levels. A sunken fontanel can be an indicator of dehydration, while a bulging fontanel might suggest increased pressure within the skull, potentially due to infection or fluid buildup. These visual and tactile cues are important diagnostic tools in early infancy.

When do fontanelles close?

Your baby’s soft spots won’t stick around forever. Eventually, the bones in her skull will build up enough minerals to completely fuse together, and those gaps will close.

The smaller back fontanelle typically closes by the time a baby is around 3 months old, but is sometimes closed at birth. The top one, however, may stay open well into your baby’s second year to give that amazing brain the space it needs to grow, though by the time your little one turns 18 months old, it should close up.

Pulsing or bulging soft spot

If you notice your baby’s fontanelle seems to puff out when she cries, concentrates on a poop or vomits, don’t panic. These can cause extra pressure to enter the body, making the fontanelle bulge out a bit. If the fontanelle goes back to normal when your baby has calmed down and is in an upright position, then all is well.

Your baby’s fontanelle can also appear to pulse whether she’s stressed or totally relaxed. Luckily it’s not a cause for concern. The temporary lack of hard covering means you’re simply seeing your baby’s blood pulse along with her heartbeat.

How do you take care of anterior fontanelle?

1. Gently Supporting the Head

Since a newborn’s neck muscles are still developing, it’s really important to always support their head and neck with your hand whenever you pick them up or move them.
When supporting their head, you can gently place your fingers on the back of their head, being careful not to put any direct pressure on the fontanelle area.

2. Avoiding Pressure on the Fontanelle

When holding your baby, please be extra mindful to avoid putting any pressure on the fontanelle.
Even a small amount of pressure can cause discomfort or harm, so it’s best to handle this area with extra care.

3. Using Proper Holding Positions

There are several ways to hold a baby, and whichever position you choose, it's important to make sure their head is always well supported.
Some common holding positions include:

• The cradle hold: Where your baby's head rests in the crook of your arm, and their body lies horizontally.
• The upright hold: Where your baby's head rests on your shoulder, and their body is in a vertical position.
  Also, it’s best to avoid any sudden or excessive movements, including shaking, while holding your baby.

4. Gentle Touching and Cleaning

During your baby's daily care, like when washing their hair or gently stroking their head, it's important to use soft and gentle movements.
You can use a soft cloth or your fingers to clean the fontanelle area, but be sure to do so delicately and avoid rubbing too hard.

When to worry about baby’s soft spot

Normally, a baby’s soft spot is firm and curves in just slightly. But call your doctor right away if you notice these rare but possible signs of trouble:

• A dramatically sunken fontanelle. This can signal dehydration, especially if your baby isn’t eating or drinking well and is having fewer wet diapers than usual.
• A bulging fontanelle with flu-like symptoms. This can sometimes indicate increased pressure in the brain due to head trauma, an infection or fluid build-up — especially if your baby has a fever and is unusually sleepy. If you notice a bulging fontanelle along with a fever or excessive drowsiness, seek medical attention right away.
• A fontanelle that doesn’t seem to be closing. Talk with your doctor if your baby’s soft spots haven’t started getting smaller by her first birthday. This could point to a thyroid hormone deficiency that needs medical treatment.

Your baby’s soft spots might seem delicate and sometimes even look a little strange. But some occasional bulging or pulsing is par for the course. And they’ll eventually go away as she gets a little older — which will happen sooner than you think!