If the soft spot on top of your baby’s head makes you a bit nervous — especially if you’ve noticed it pulsing or occasionally bulging out a bit — you're not alone.
But while they may look vulnerable, these soft spots (called fontanelles) have a special purpose. And just like so many other aspects of the newborn phase, they won't hang around forever. Here’s what you need to know until they close up completely.
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 anterior fontanelle. 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.
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.
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.
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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.
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.
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.
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