A place of business has the right to any dress code they like, but if it were my grocery store, I would allow for PJ's at the appropriate "bedtime" hours. One would expect a new parent with bloodshot eyes slumping into the store at 2AM for diapers and a bottle of pain killers to be beyond niceties such as daytime clothes. If you are at the store at 2AM, then you are not among the decent people of the world, anyhow. And I completely agree that a pregnant woman in her last trimester or postpardem should feel completely justified in wearing comfy pants and soft slippers anyplace she pleases, at any hour.