The soft spots on your baby's head can feel alarming to touch — but they serve a critical purpose. Here's everything you need to know about fontanelles.
What Fontanelles Are and Why They Exist
Fontanelles are gaps between the skull bones that allow the skull to flex during birth and expand rapidly during the first year of brain growth. Without them, the brain could not grow at the extraordinary rate required in early infancy.
The Two Main Fontanelles
| Fontanelle | Location | Size at Birth | When It Closes |
|---|---|---|---|
| Anterior (front) | Top of head, toward front | 2–3 cm wide, diamond-shaped | 12–18 months |
| Posterior (back) | Back of head | Less than 1 cm, triangular | 6–8 weeks |
What Normal Fontanelle Feels Like
The anterior fontanelle feels soft and may pulsate gently with the heartbeat — this is normal. When the baby cries, it may bulge slightly. When the baby is upright and calm, it may look slightly sunken. All of these are normal variations.
Sunken Fontanelle: Dehydration
A fontanelle that appears significantly sunken and does not refill when the baby is laid flat suggests dehydration. Look for other signs: fewer than 6 wet nappies a day, no tears when crying, dry mouth, and dark urine.
Bulging Fontanelle: Red Flag
A tense or bulging fontanelle that persists when the baby is calm and upright is a warning sign of increased pressure inside the skull. This requires immediate medical assessment. Causes include meningitis, encephalitis, hydrocephalus, and other serious conditions.
Emergency
A fontanelle that bulges when the baby is calm, particularly with fever, vomiting, sensitivity to light, or a stiff neck, is a medical emergency. Go to hospital immediately.
Is It Safe to Touch the Soft Spot?
Yes. The fontanelle is covered by a tough membrane — the scalp and underlying tissues protect the brain from normal handling. Normal touching, bathing, and gentle brushing of hair over the fontanelle are safe.