The Reason You Have An Innie Or Outie Belly Button

Referring to an "outie" belly button, Jennifer Shu, M.D., FAAP, an Atlanta pediatrician, co-author of Heading Home With Your Newborn: From Birth to Reality, and spokesperson for American Academy of Pediatrics, told Real Simple, "The skin just chooses to grow in an outward direction rather than inward." 

Dr. Curtis Cetrulo, Jr., a plastic surgeon at Massachusetts General Hospital in Boston, agrees, explaining to NBC News that the amount of space between the skin and the abdominal wall often determines which way your belly button will grow. If there is less space, soft tissue will most likely protrude through, pushing the remaining umbilical outwards and ultimately creating an "outie" belly button.