<s>[INST] during the birth of my second child his head circumference was 3cms less than the normal. Dr s told this is primary microcephaly .Now he is 2years old all his activities are normal he speaks identifies objects and does everything normal but looks smaller than other kids of his age group [/INST] Hi, Welcome to Chat Doctor. Kindly don't compare with other child Chat Doctor.  The right way to do it is to compare in the children growth card how he is doing. If his head size is growing in the normal means as plotted in his growth card, and he is otherwise developmentally normal, I don't think you need to be worried. Head size is a depiction of brain growth inside and if rest are normal, then brain growth also would be normal. Hope that answers your query. Take Care. </s>