Kate,
Congratulations on Baby Number 3. How old are your other 2 children? 
I took the advice from another post when I was pregnant last year.
It was from a woman who had three kids and was in great shape.
She attributed to using the " Perfect Pregnancy Workout." 
The instructor is a professional acrobat who is also 8 months 
along. I bought and used from my first trimester until the end.
I found it effective, highly actually. I am an advanced exerciser 
but it did challenge me. The weight came off quicker than my last 
pregnancy and my stomach muscles were in great shape. I had 
tried all the other DVD'S. You name it I have. I also have to say
not too many people liked Leisa Hart's Fit Mama but I loved the 
20 minute Yoga section. It actually felt great and helped me stay
toned. 
Good Luck!!! 
Jennifer Claire 12/24/05
Taylor Elizabeth 8/22/07