We went through this with our mare. We bought her supposedly bred, bloodwork said no, but she was clearly pregnant and an ultrasound later confirmed it. She wasn't a maiden mare (two foals that we know of and red bagged her last one), but she went well beyond her due date. Never waxed up and even had the yellowish "milk" to the day before she foaled. We stalled her a couple of weeks before she foaled Remi. Mares don't like playing by the rules
Keep us posted
Keep us posted