I've heard anecdotal evidence that some people can, yeah. I remember one MDC mama saying her oldest daughter could always tell when she was pregnant by sniffing her mother's coat! Remember, lots of mothers don't know they're pregnant for a good 5-6 weeks or even longer, so they might be showing subtle physical signs, or giving off unusual pheromones, or something which an intuitive person could pick up on.
I also remember watching The White Masai (movie based on a book, based on a true story). In the movie, the white woman was told she was pregnant by some Masai women, after they felt her skin. They were right. I'm not sure how factual that was though - I don't remember that incident occurring in the book, but maybe I just forgot it?