I did it in my 8th month. That is what my nurse recommended.
We did it in the middle of my third trimester. You should sign up ahead of time since those classes fill up fast in some places.
Yes, I agree with Yvette. Depending on the length of the class (usually 4-6 weeks), I'd start toward the end of month 6 or beginning of 7. You just never know when that baby will make his appearance! Plus, I didn't feel like lugging my big self to classes when I was eight months pregnant...lol. Do it while you still have energy! :-)
Tricia
Whever you are thinking of taking it...check with them and see what they recommend. It varies from place to place. Probably take during month 6 or 7 is a good time. Early in your third trimester is when I did it from what I recall.