When Does the Posterior Fontanelle Close?

The posterior fontanelle usually closes by age 1 or 2 months. It may already be closed at birth. The anterior fontanelle usually closes sometime between 9 months and 18 months. The sutures and fontanelles are needed for the infant's brain growth and development.

Which closes first anterior or posterior fontanelle?

The posterior fontanelle usually closes first, before the anterior fontanelle, during the first several months of an infant's life.

What happens if the posterior fontanelle doesn't close?

If the soft spot stays big or doesn't close after about a year, it is sometimes a sign of a genetic condition such as congenital hypothyroidism.