The fontanel is the baby’s bones are not well developed, so that the skull and the skull is not tightly integrated between the skull, and the skull gap, the baby 1.5 years old fontanel is not closed is generally a normal physiological phenomenon, strengthen the nutrition, observation and follow-up can be. Babies are born with two fontanelles, anterior fontanel and posterior fontanel. Some babies are born with closed posterior fontanelles, and those that are not closed usually close at 6 to 8 weeks. The anterior fontanel will increase in size with the development of the brain when the baby is about 6 months old, and then it will slowly become smaller and smaller, and most normal babies will close it within 24 months. If your baby is over 3 years old and the fontanel is still not closed, you need to be on high alert for delayed closure of the fontanel, and it is recommended that you seek medical attention as soon as possible.