Hi! welcome to HCM! A newborn has six fontanels,the anterior and posterior, two mastoid, and two sphenoid. The anterior fontanel is the largest and most important for clinical evaluation. The average size of the anterior fontanel is 2.1 cm, and the median time of closure is 14 months. The diagnosis of an abnormal fontanel requires an examination by a pediatrician and imaging studies if required,as there is wide variation of normal. .A physical examination helps the physician determine which imaging modality, such as plain films, ultrasonography, computed tomographic scan, or magnetic resonance imaging, to use for diagnosis. Fontanel closure that occurs as early as three months of age can be within normal limits, but careful monitoring of head circumference in such cases is essential to exclude a pathologic condition. The fontanel sometimes can be open but difficult to detect during a physical examination. Craniosynostosis and abnormal brain development are associated with a small fontanel or early fontanel closure. You must get your child examined just to rule out any pathologic condition. hope this helps!