You're welcome!
I should say though that Hi/Lo Heaven is the name of Christi's newest tape that was just filmed last week and won't be released until July. So obviously I don't know anything about that tape or whether it could be modified (from what I understand, it has some intervals in it, so that clearly wouldn't be appropriate for pregnant exercisers at any level of fitness). The one I was suggesting was her one from last summer--Happy Hour Hi/Lo.
Also, Gay does have a pregnant exerciser in the STEP portion of her 2K01 video, but not the hi/lo portion (although the male exerciser seems like he gets pretty pooped out toward the end there and keeps everything pretty much very low impact, so you can follow him for modifications as you need to).
With those clarifications, good luck!