I was told not to at 35 weeks but at 38 weeks I was told I could (contractions had started as well though). I would if labour has started and you are term and no other probs eg GBS. If labour not started have a shower instead.
Aren't birth pools supposed to be sterilised or something?
My hospital's policy is that if contractions haven't started within 24 hours, you have to be induced to reduce the risk of infection anyway, so I can't see that having a bath would make much difference either way!
I'm a midwife, if that makes any difference. Its fine to have a bath as long as the temp is not too high (should be round 37 degrees celsius - but don't fret if you have no thermometer!). Dont use any bubble baths etc. Water can help stimulate contractions so good luck!