Dear Mustafa Aslam Awan:
Your pediatrician has a head growth chart and you should be able to get one from him/her. Whether 47 cm is a large head at 4 months of age, the answer would be yes. The average head size at 4 months is 40 +/- 2 cm. If you have been measuring the head size for the last few days and it is visably increasing, I would tell your neurosurgeon. Hydrocephalus signs would be a change in mental status such as increased irritability or lethergy. This could be episodic in nature, there could also be vomiting. I would call your neurosurgeon and pediatrician.
Sincerely,
CCF Neuro MD