Newborns should poo more often than an older baby. By about 4-6 weeks it's normal for poo to be less frequent, but for younger babies they should poo several times a day ideally. However, my 8 month old didn't poo between days 2 and 7, and it was just his body using everything up. I was worried, and I made sure to keep a close eye on his weight gain and his urine output. It's not 'normal' for a newborn baby not to poo, but it can happen and be fine, or it might be indicative of a transfer problem, or a supply problem. Keep an eye on everything else and if you're worried at all go and get LO weighed and see what's going on. It's pretty much definitely not constipation, though, so don't go down the boiled water or prune juice methods some recommend online.