When babies are born, the skull is not yet fully developed, the articulation between bones is not tight and there are gaps, forming two areas at the top of the head and the back of the occiput that are not covered by bones, known as the fontanel and the posterior fontanel respectively. The closure of fontanel is a window to reflect the brain development. Under normal circumstances, the closure of fontanel occurs between the age of 1 year and 1.5 years, and the closure of posterior fontanel occurs 3 months after birth. Early or late closure of the fontanel is a sign of abnormal growth and development. Early closure of the fontanel: If the fontanel closes before 6 months of age, the child may have microcephaly or an underdeveloped brain. Late closure of fontanel: If the fontanel is not closed after 18 months, it is considered late closure. Late closure of fontanel is mostly seen in babies with hydrocephalus, rickets and cretinism. Due to individual differences, the baby’s fontanel closure time will be slightly early or delayed, as long as the measurement of the baby’s head circumference is normal, the general head circumference at birth is about 32 ~ 34cm, about 42cm at 6 months, about 46cm at 1 year old, about 48cm at 2 years of age, if the head circumference is in the normal range of values, generally does not affect the development of intelligence, parents do not have to worry too much, if the fontanel closure of early, you must measure the baby’s head circumference, if the fontanel closure of early, you must measure the baby’s head circumference. If the fontanel closes earlier, you must measure the baby’s head circumference, as long as the head circumference is still growing, there is no need to be anxious, if the head circumference is lower than normal, it may be cerebral hypoplasia, you should go to the hospital for further examination, please ask the doctor to identify the diagnosis. You can give your baby some calcium and vitamin D supplements as appropriate, and take your baby to sunbathe more often, which will help your baby’s growth and development and the closure of fontanel.