In some ways, this is the easiest of poses and certainly an obvious choice. Once your subject is feeling comfortable, it is mostly a matter of having her show off her belly. It is so simple you might wonder why it isn't first on the list. I've put it second because it works better if you transition from the cradled belly to this pose. These two poses have much in common, but they are not the same.
While you do not need to restrict yourself to an order for these poses, this one should work better after the cradled belly — after you taken a few photos and the mom-to-be is feeling more comfortable in front of the camera and you have found a rhythm.
You want the mom to feel more confident and relaxed because her expression is very important to this pose. If the mom looks happy, or thoughtful, or self-concious , that is what the photo will be about.
This pose is easier to do in a 3/4 view than in a strict profile. This is because the mom is showing her belly to the camera and thus is interacting with the viewer in the photo. If her belly is at a perpendicular angle to the camera, the interaction is transferred entirely to the face. However, a strict profile of the belly is definitely worthwhile. It is a great way for the mom-to-be to show off her pregnancy and is a traditional way do demonstrate how she is carrying.
A more dynamic posture tends to work best with this pose and it can be exaggerated for effect.
As with the "Cradled Belly" pose, the placement of hands may be used to help minimize or hide any unwanted bulges in the mid to lower back. The placement of the mom-to-be's hands can help to get a more flattering pose.
Depending on the confidence and comfort level of your subject, she may face a little bit a away from the camera and twist back. This, however, is not a pose that works for all moms-to-be.
This photo has a very different focus and meaning than the photos above. If your subject is the rare mom-to-be who is "all belly" and she has expressed that she wants to show that off, you can use this pose to transition to a I-don't-look-pregnant-from-behind photo.