What is the normal size of the baby's anterior fontanelle?

When babies are born, their fontanelles are not completely closed. This is a normal phenomenon. Generally, they will slowly close during the baby's growth process. This is also a normal phenomenon after a baby is born. However, many parents are particularly worried and do not know what the normal value of the baby's fontanelle is. Some parents also check whether their children's condition is normal. What is the normal size of the baby's fontanelle? Let’s take a look at it together.

The normal oblique diameter of the baby's anterior fontanelle is 2.5 cm. There is a soft area on the top of a baby's head that can sometimes be seen to pulsate, which is medically called the fontanelle. There are two main fontanelles at birth: one is called the static fontanelle, which is located in the front part of the head and is formed by the connection of the anterior superior angles of the parietal bones and the frontal bones on both sides. The oblique diameter at birth is 2.5 cm and it is generally closed at 1 to 1.5 years old; the other is called the posterior fontanelle, which is formed by the junction of the parietal bone and the occipital bone. It is located in the back of the head and is generally very small or closed at birth. It closes at the latest at 2 to 4 months.

When a baby is born, there are two boneless "windows" on the top of his head, which are medically called "fontanelles". The posterior fontanelle usually closes 3 months after birth, while the anterior fontanelle does not close until 1 and a half years old. The "skylight" or "fontanelle" that people often refer to mainly refers to the anterior fontanelle.

The surface of the fontanelle is the scalp, underneath it is the meninges, and then the brain and cerebrospinal fluid. Place your finger gently on the fontanelle and you can feel the beating. That is because the cerebrospinal pressure changes with the heart beat and blood pressure, which is consistent with the pulse. When a normal baby is sitting, the fontanelle is slightly sunken.

The cerebrospinal fluid in the skull is constantly exchanged with the body's blood and tissue fluid to maintain balance. When the body loses more water, the cerebrospinal fluid in the ventricles will also decrease, the pressure will decrease, and the fontanelle will become noticeably sunken. If an infant develops this symptom after vomiting or diarrhea, it means that the body is already moderately dehydrated and must be replenished with water in time. Otherwise, due to the infant's poor natural adjustment ability and insufficient tolerance, circulatory failure may occur, which is life-threatening. Extremely thin infants with severe malnutrition due to improper feeding may also have a sunken fontanelle, and at this time, they need to strengthen nutrition and feed properly.

Through the above introduction, we now know the normal size of the baby's anterior fontanelle. This is also a judgment of the baby's development standards. Generally, there is no problem with the child. It will grow completely and close after a few months. In normal times, we must pay attention to the child's nutrition, and the fontanelle must also be protected from the wind.