Fontanelles, so named because the pulsations that can be felt through this thin membrane were once thought to be “little fountains,” are tougher than we realize. It’s natural to feel a bit neurotic about damaging your baby when older women tell you not to touch these soft spots, but they really are quite harmless. The posterior fontanelle (which you’ll find towards the back of the skull) is roughly triangular in shape and usually closes after 12 weeks.
I find that mothers are not as aware of this fontanelle as they are of the anterior diamond-shaped soft spot on their baby’s skull that closes from one year to 18 months. By all means, be gentle when washing your baby’s hair, and gently massage the area covering the fontanelle with the pad of your finger. If it’s neglected, this is where cradle-cap or dermatitis can develop when dead skin cells are not washed off. You can use a soft baby brush to brush your baby’s hair – especially if it is quite thick.