They could not care less if you are carrying diapers. As long as it's not illegal (drugs, smuggled goods, large sums of cash, etc) or a safty issue (fireworks, certain batteries, anything highly flammable, etc) diapers would not call into either of these categories. Even in you carry on, I have had tsa search my carry one with three or four diapers in it. This was right after 9/11 and my cheap company purchased two one way airline tickets. I was selected for extra security for every leg of that trip. Four tsa agents each carefully inspected my carry on. They removed most of the items so they could see everything, but they never removed the diapers. all of them saw the diapers and completely ignored them. To the extent that the other employee who was going through sedlcurity with me couldn't see anything either.