A robust male baby with vigorous feeding and immediate vomiting at 2 months of age. Most probable diagnosis is

Congenital hyperophic pyloric stenosis is seen between 3 rd and 6 the week of age of an infant because the time taken by the hyperophied muscle to cause complete obstruction is between 3rd and 6 the week, as well as the congenital hyperophic pyloric stenosis is most commonly seen in firstborn males. Reference: SRB 5 the edition page no. 821