Colors are nice. Her expression seems a bit strained and the free-flying cloth is cut off rather abruptly, both of which detract from the happy sort of feeling I would expect to get from this kind of shot. But then I don't think a pregnant woman ever feels totally free, inhabited by another being as she is, particularly at that stage where the being is making him/herself known via kicks, stretches, hiccups and the like.
I see what you are going for on this shot. I think that the horizon could have either more crooked or strait to help the image a bit. Also I would have probably dodged your subject a bit in PS to add some light to the underexposed areas. The tone of the grass is fantastic and your blue sky really works well. I think that a little bit of dodging and burning would make this image stand out a little more.
lovely shot anyone would be proud to have that on their wall. but there is somethign bothering me, and i am not sure what it is, maybe the creases in her pants, maybe the not so sharp figure, maybe the angle.