Here are my thoughts
1- The composition is a bit off. Seems like you are not close enough and not far enough out. I dont like the tree in the background and how her elbow intersects with it. The shadow on the ground is odd as well.
Maybe playing with the shadow would help...as in step more to your left to include the shadow in the image... if its in there, use it for something. Heck, even trying to get her positioned so you see the belly in the shadow would be cool. The pose is ok, although there seems to be some blurryness around her elbow and bottom right of the dress. Did you do some post blurryness on the image?
2- the pose is nice, and having the tree here works (not like in the first) as it kind of helps frame the subject. Do you really need it? Maybe not, but it adds that extra element in the shot to help balance it out. Not sure I like the leaning on the right arm though and the overall processing seems a bit dark. I prefer lighter, more lively images for maternities. Might be my work monitor though
3- Yeah, upside down heart like that...no. The more traditional heart can work in some shots. I dont like the crop on this one. Shooting portrait instead of landscape would help minimize the background, which is just adding empty space for nothing. Portrait and in close. Love the model's hair and the colour of her top and jeans, nice work there.
4- This one I really like, my fave of your set. Clean, simple. I like the flare from the sun and how just part of her hair is light up. Nicely done
5- This one just looks uncomfortable. I dont like angles that are like looking at someone just standing there snaping. Getting down low and making a more side profile shot would be cool. You cut off part of her hand, which looks to be in a very odd position. I dont like the processing either, looks a bit dirty and dark.
One overall comment is that none of these have her looking at the camera. I understand the feel of intimacy having her not look at the camera can create, but have her look at you and get those eyes in the image, that is how people connect with a subject and an image, is through the eyes. So throw in a mix of looking and not looking