A small fontanel in a newborn needs to be determined firstly whether it is anterior or posterior fontanel, if it is posterior fontanel it is normal, if it is anterior fontanel it is abnormal. There is a difference between anterior and posterior fontanelles in newborns. The posterior fontanel is usually only the size of a fingertip and will close completely around 6-8 weeks after birth. A newborn’s fontanel is about 1.5-2.5 centimeters in size and usually closes around 12-18 months of age. If the fontanel is less than 1 cm it is abnormal and parents should take their child to the hospital for examination and treatment. The size of the fontanel, the time of fontanel closure, and the head circumference of a newborn is an important indicator of the newborn’s physical development and health. A small fontanel in a newborn may be caused by brain dysplasia, microcephaly, brain disorders, and early closure of the fontanel. Parents are advised to observe their newborn’s fontanel from time to time during the growth period, and seek medical attention when abnormalities are detected.