If you can, try to get her back for another shoot later in her pregnancy. I like where you're going with these and they'd benefit from the bigger belly.
1. I like the composition, and I like the pose (maternity shots are about the only time you can get away with the hand-bra). I like your intent with the lighting (well-lit belly, nicely shadowed backside). I think you need to get more vertical coverage with your lighting so that her face gets some more light. Between the bright belly and the light colored hat her face looks dim.
2. This is the shot which really needs the larger belly. As it is, lying on her back has caused her stomach to drop and spread out to the sides - it just looks like she has a solid spare tire, which (looking at shot 1) is certainly not the case. I'd suggest shooting this more down her length than almost square from the side. That way you'll be able to get the focal elements closer together (her face and the booties on her belly). As it is my eye is torn between the upper right (bright white booties) and lower left (nice white eyes). You'll also not be shooting her arm square on - her upper arm looks appreciably larger and fleshier than in shot 1. Alternatively, you can get in closer and shoot just the belly with the booties (again, that would benefit from a more pronounced bump).
3. I like the concept of this shot, and I'm sure she was glad to get a nice shot of her ink before belly stretching did anything to it. I agree with you that it is too dark. This is probably one time you want to get away from your use of shadow and light from both sides. The ink is closer to wrapping around her back than going across her belly, so you certainly want to illuminate that side well. But you also want to highlight the curve of the belly as well as you can rather than letting that blend into the shadow. Between the overall darkness of the image and the belly blending into the shadow, this is another case where it's not as obvious as it could be that she's pregnant and not just out of shape. I'm guessing that this was earlier in the shoot, before she got comfortable enough to go topless (the redness running through "Serenity" is from a recently removed bra)? I think this would work better either without the fabric up top (show just some breast, stopping below the nipple) or with a nice silk or satin bra which matches the ribbon (if you can find one which is cut so it doesn't cover the ink). Oh, and I'd say go rule of thirds on this one!