Pregnant woman are a tough one to get, to show the bliss on her face and the baby growing, so I’m not going to comment on the cropping. Pregnancies are out of my league (except when it came to getting my wife pregnant) so I honestly don’t feel qualified to be able to comment too much on the overall shot.

On the lighting
I really feel that the subject needs some sort of seperation from the background especially for her head. Her hair just disolves into the background which, when you consider how big a body is compared to the head, makes a relatively small part of the subject smaller. Maybe a smallish reflecter at head hight just to give definition to her head (separation from the background).
The angle of the light also throws a shadow on her (right) arm from her breast. Maybe just a slight turn further into the light is all it would take to resolve an issue like that.

Her face
Her head is neither in profile nor turned toward the camera. It gives that “contemplative” look. I have mentioned this before but have had no examples to demonstrate it and now I have:
DO NOT CUT THE CHEEK LINE WITH THE END OF THE NOSE!
Why? Because I said so that’s why :O
Actually, it’s to do with the orbits of the eye. When the end of the nose goes past the cheek line (this is to do with teens and adults, babies heads are different) the far eye becomes partially hidden by the bridge of the nose and the eye socket is not complete so that the eye hangs in space. In a profile, the far eye socket is not visible and is therefore irrelevant. If you look closely at the face of Lillian, her pupil disappears into the background and this can be bad form for portraiture.

I’ve cropped this (from a screen capture) so that others can see what I’m talking about. If her head was turned toward the camera just a fraction the tip of the nose would come back within the cheek line and the outer edge of her far eye socket would then enclose her eye giving her eye completeness. From there it may be advisable to tilt the top of her head a fraction towards the camera and then the bridge of her nose would not hide any of her far eye.

So there you have it. I can see why you like this photo so much. These are just things to look out for.