Anyone know the science behind "popping"?

Leslie
I am curious if anyone knows why babies "pop" as opposed to your belly just getting gradually bigger every day. It seems crazy to me that one day you are barely showing (usually just bloat) and then all of a sudden, boom!, there is a baby belly. And if it is so sudden why don't we feel a major shift (or did you?) when it happens? Just random curious pondering over here...