they say Brigitte Bardot had a 20 inch waist. some other models claim even lower.
18 is definetly not impossible

anyways Im feeling very gay talking about this, real men discuss biceps and chest measurements only
35.5B-19-35, in And God Created Woman 36B-20-35
But all pics, seem to be taken with a belt cinched right around her waist, squeezing it, like a corset.