Your son seems to be fine neurologically and at the age of 14 months his head size is 44 cms. Some babies may have smaller heads specially if there is family history of small heads. If the baby is other wise fine nothing needs to be done. But if your son's X-ray shows fused sutures it should be confirmed by a CT scan in consultation with a neurosurgeon. When a baby is born the skull is formed by mainly four bones with sutures in between. If there is an early closure of sutures which is called craniosynostosis the head may stop growing. There is no harm in having a consultation and investigations, and if they come normal you can forget about it.