Bending in pregnancy?

I like to read all these pregnancy books, but at the same time I don't.. I mean, there are just some things that they suggest that don't make sense. I am 5 months pregnant and I bend at the waist. They should specify "if it makes you uncomfortable", or, "don't do it because it's dangerous".. they just tell you don't this don't that. Don't worry, the only reason why not to bend at the waist is because it might make you uncomfortable as your belly gets bigger and bigger.. that's all.