My 4 month old son has not had a wet dyper in over a hr?

Is he feeding?: If he is feeding / drinking at or near his usual rate, then it will catch up. But, if he is not peeing because he is not taking in fluids, that can very rapidly become a big problem for little people, as they have almost no reserve. If not drinking and not peeing, head to er. If will drink juice / pedialyte / formula, then wait a bit longer for a "big one.".

Other symptoms?: Assuming he is otherwise feeding well, it is typical for an infant to have 5-6+ wet diapers in a 24 hour period. I would not be worried at this point if it has just been 1 hour. If, however, he has not been feeding well, has a temperature, or has new vomiting, i would call your health care provider.

Monitor: A 4 month old should have 5 or more wet diapers per day. Continue to monitor, especially if there is diarrhea, vomiting, or high fever; dehydration can creep up quickly. If the diaper remains wet after 4-6 hours even with increase fluid intake you should seek medical attention.

Confusing question: I expect an infant that age to wet every 3-5 hours. If you were changing more often earlier, I consider that odd and would wonder if you are over vigilant or actually seeing pee. If the kid is robust and playful, things are probably okay.If the kid is tired and less active, see a doc soon and review everything that has been going on.