I agree with mandyatm, the first one is very nice. You did a good job with the lighting and the butterfly was a nice touch.
The second doesn't do much for me, it doesn't strike me as much of a maternity shot and could have been just a regular budoir shot. The third one is a good "almost there" shot. It is a good, standard maternity pose--one of those "must-do" shots--but you cut her head off at the neck, which ends up looking weird. Also, this type of shot works best without the panties. The lace panties detract substantially from the shot as the patern clashes with the draped cloth and they overemphasize the larger form of the pregnant woman in an unflattering way. As a nude, the dangling cloth helps to soften the outline the woman in a pleasant way, showing she is pregnant without being overly obvious about it. This pose also looks great as a full-figure silhouette--with and without the draping cloth. Finally, I wouldn't worry about a little noise. It actually enhances most black and white shots. Embrace it and find ways to make it work for you creatively!