RE: step vs. hi-lo: which is best for childbirthing mus...
Well...don't get me started! I got Birgitta Gallo's book Expecting Fitness and there are many, many exercises in there. It's an excellent book and I'm sure you could get it used on Amazon like I did--it's one of the most highly rated pregnancy exercise books out there. Some of the exerercises are "loosening up" type exercises to stretch and loosen the hips, pelvis, etc., and others are strengthening exercises. She makes a distinction between the need to loosen certain areas (vs. strengthening them) and the need to strengthen certain muscles. I know I haven't been very specific, but it would take pages and pages to tell you about them all.
I also read Exercising Through Your Pregnancy by James Clapp, one of the most well-known pregnancy exercise researchers who poo-poos many of the very conservative exercise rules for pregnant women that many obstetricians currently hold. I'm at 7.5 months and am still hopping around doing step and hi-lo and have had no problems whatsoever, so I think he's right on track. I have very few aches or pains compared to other women at this stage of pregnancy, so I think he knows what he's talking about.