My newborn hasnt pooped in 24 hours and he used to poop almost every changing, should we be concerned?

No: As long as he is comfortable and has no other symptoms, such as vomiting and abdominal distention with firmness, he is likely OK. He may also continue to pass some gas. There is a huge variation in what is considered normal stooling frequency. All the best.

Breast or bottle ?: Breast fed babies can have a little smear with each feed or have one big blowout every 7-10 days.Bottle fed kids will poo more predictably & should go daily. If the poo is soft it is not considered constipation. I don't get hung up on babies timing, I like to look at them to see how they feel.