Are you talking about innies vs. outies? These are actually not caused by any human intervention with how the umbilical cord is cut or treated after birth, that's a common misconception. So good news, you can time travel and not get clocked as a futurian because of your fancy navel. The innie shape just forms naturally, and outies can be caused by a tiny infection at the base of the cord, or a small hernia. As this should probably be kicked over to AskScience anyway, try this AskScience thread from the archives.