baby constipation

My little princess got her 2 month shots last Thursday. It's been a little over 24 hours since she's gone poo poo. This is very abnormal for her as she normally goes 2-3 times a day. She's noticeably more fussy and I think it may be due to constipation. I heard to not be concerned if a baby does not go poop until it's been 4 days. Is this still the case of their regular bowel movement is 2-3 times daily?