Soccer Ball?

I got my 24 week update email yesterday and it said that my uterus is the size of a soccer ball. As a soccer nut and coach it makes me wonder... What size soccer ball?  Is it is a little kid's size 3 soccer ball? Or my size, a size 5 soccer ball?  I wish they would specify... I'd like to know! :)  So if the baby is the size of a corn and my uterus is the size of some sort of soccer ball... no wonder I look the way I do! :)