I hope this question isn't offensive, but those who know someone who didn't find out til they were like 20+ weeks - were they quite big ladies?

After 2 babies I just can't comprehend not realizing...
Nope. My cousins daughter was a size 8 Being her second baby you'd think she'd know the signs too but she hardly gained any weight, her periods continued and she felt pretty well and normal. It's so hard to fathom!