This is an interesting question, and I can imagine an answer that discusses how Thomas being propelled through a dark tube (elevator shaft) and suddenly being exposed to light is quite similar to what physically happens in an actual birth. Beyond that, Thomas's emergence from the elevator is mentally symbolic of a rebirth. He is a new person in the Glade because he does not know anything about who he used to be. All that he knows is his first name. He doesn't even know his last name.
And yet he didn’t know where he came from, or how he’d gotten inside the dark lift, or who his parents were. He didn’t even know his last name.
He doesn't remember his parents, his former friends, or anything else about his past life. The Glade, and the surrounding maze, is an entirely new world to him with societal rules and a hierarchy that he must relearn. Thomas even has to learn a new language. The Gladers do speak English, but they have an entire vocabulary that Thomas has to figure out. The lack of self knowledge combined with the newness of everything is quite similar to what a newborn child is faced with for many months and years to come.