Hi there,
I'm only in the first trimester of my pregnancy, so I am not speaking from recent experience here, only with what I plan to do for myself in a few months time. The CTX series is a great series, particularly if you don't have a lot of time to exercise. However, the cardio segments are at a pretty fast BPM, and include a lot of intense moves in order to accomplish alot in only 30 minutes or so. Based on how I felt after I had my first daughter 4 years ago, I consider CTX to have too much intensity for the immediate postpartum period (LOTS of power 7s, double-ricochets, plyo-jacks, jumping jacks, airborn jumps, power scissors, etc). I'm remembering how weak my pelvic floor was after having my baby, and how that kind of impact would have been intolerable at the time. Having said all that, CTX's All-Step is a terrific, rather easy, mostly lo-impact step workout without a lot of intense moves, until the "blast" at the very end.
I would suggest that you get the Body Blast DVD series, if you don't already have it, because her workouts in that series are super flexible, allowing for a very wide range of fitness levels - each DVD has so many premixes ranging in length from 20 minutes to 2 hours. The TimeSaver DVD would be a great alternative if you don't want to get the whole BB series. IMO, the BB series is also her most fun. It would allow you to gently acclimate your body back into aerobic workouts, while also giving you more advanced workouts when you feel ready for them.
I've preordered the HardCore series, and anticipate using it to help motivate me to get back into shape after this baby is born at the end of March. However, I anticipate that I will have to modify, modify, modify for a while, and will probably also go back to Cathe's classics, such as Step Jam and Power Max, done on a 4 or 6" step, probably taking out the impact. Any workout would suffice, really, as long as you listen to your body and keep your expectations at the beginning very low.
Best of luck with your new baby!!!
Sandra