Hi there, congradluations!!!
I am another voice of experience saying "if at all possible go at a different time." 8 months pregnant and Aug at WDW doesn't mix.
I have been to WDW pregnant 3 times (2 pregnancies)
1st one was 32 weeks pregnant, it was 1st week of Febuary 2001, baby was born on her due date March 29. All went well, it was a great trip. I felt the best I did the whole pregnany. I am so glad we went. My Dr. supported it fully, however after 35 weeks travel is discruaged or even forbidin.
2nd pregnacy the 1st trip I was only 8 weeks (about a year ago now) and we had planned the trip before the pregnacy. We also took another trip in May 2004 (but we really only went to Vero Beach and DTD, not the parks) but it was a great time. I was 26 weeks and it was one of the best vacations ever. Far enough along to stop being sick, but not that big yet (or at least not nearly as big as I was going to get, Baby was born Aug 3rd.) The weather was just wonderful in May.
We went Aug 2003 and decided never to go back in Aug again. Not only the heat but the rain was terrible. Last Aug was all the hurricanes. Rethink Aug if you can. May would be great, or early June if you can.
So here is my recomondation, go, take one (or even two) last vacations before the baby comes. There is a ton you can do at WDW pregnant. But if there is any way possible go at a different time, and don't go after 35 weeks. When I went at 32 weeks I don't think any later then that would be good (techically I had started the 8th month, out of 10)
Best of Luck!