Happened to a teacher when I was in junior high. One day she didn't show up, and they told us we'd have a sub for the rest of the year. That the teacher had gotten "sick". Well, she hadn't gotten sick - she went to the ER for severe abdominal cramping, and came home with a baby. Nobody knew she was pregnant, including her.
And yes, she was HUGE. So was her husband. How exactly that baby came to be is the stuff of teenage nightmares 😛