Asking for a friend. Just kidding. I am on my way to Disney World and I know about all of the warnings and I'm not planning on getting on any roller coasters (maybe the Kilamanjaro Safaris, but no Thunder Mountain), but I've always wondered why you aren't supposed to and it seems the major concern is placental abruption. Definitely very serious and scary, but I haven't found one instance of it actually happening. So it just made me curious if anyone else had?