Contrary to many on this site, I do like maternity images (when not boring and cliche), and overall I like this set. You're lucky to have had such an adventurous mom-to-be. I think her expression in most of them comes across as peaceful/serene (or maybe a bit tired, which is understandable for any woman that pregnant), not depressed.
I generally like the lighting you used. The OCF in the first two kind of comes across as if she is standing in a beam of sunlight in an otherwise shaded forest, which works. In the third one I would have balanced the light a bit more between ambient and strobe and/or gelled your strobe to achieved a closer-to-natural balance. As it is, though I really like the lighting as it illuminates her, she seems out of place (too bright/wrong color temp to match her surroundings). I like the lighting in the next two (4&5), how you used the setting sun behind her. The lighting balance in 5 is much more what I was talking about in 3 - she has clearly been illuminated, but at a quick glance you can't tell if it's necessarily OCF or possibly a reflector, which tells me the balance is much more natural.
A few suggestions about posing. For the most part you did well. In #1 the overall pose is great and would work for a nude in the woods, but her belly is square to the camera. With the shear running across her lap and up both sides, you can't really see any curve to the belly that says maternity shot. In #2, had you switched her feet (right foot straight down, left foot out in front), her va-jay-jay (handing over man card now if you catch the reference) would have been obscured by her left thigh and you wouldn't have needed that obtrusive trail of fabric tucked through there. I'm undecided how I feel about the pose in #4 & #5. It works fine for me from the angle of #4, I like the angle of the torso/belly and the head tilt. But in #5 there's something about the dark blue being spread out and completely obscuring her legs, as well as the light blue being both overly voluminous around her breasts and sleekly trailing off behind her, that seems out of place. Not sure how I'd recommend to do it differently in that setting, just sharing my gut reaction.
On a side note, maternity shots are the only time I don't mind the hand bra, either the single-arm-bar or the two-hand-grab. In glamour shots it comes across as contradictory ("I want this shot to be titillating, but not really."), while in maternity shots it seems like the subject is just trying to show off as much of the natural process as she's comfortable with.
One negative comment...zap photo six now! With that perspective and focal length, her feet and legs look huge and completely dominate the image. Even once you get past them, the lighting draws you right up to her face. Between all that and the fact that her belly is square to the camera and relatively dimly lit, it almost takes effort to catch that this is a maternity shot.