The P90 system itself was made before P90x and is a LOT more low key. If you'd like me to show you a bit of what the workouts are, I can bring the dvd with me somewhere and show you what I mean. P90X is the more intense movements, longer workout session.
As a point of reference, my fiancee' just gave birth to our son May 5th from an emergency C-section and she is on the later part of the P90 workouts, almost to the X and has been doing it for a couple months now. So I say if someone like her who got up to a pretty hefty size with the kid which is to be expected and not being able to really do much of anything for about 12ish weeks (6-8 weeks for her to be able to move around without worrying of ripping anything and another 4 to feel quasi normal again), you can as well - especially if you're already training with someone