I like the idea, but agree that the shot is a bit blown out.
Did you use a blur? If so, maybe just take the blur off.
I can assure you the couple will know it's not a wedding photo, and cherish it. That's really all that counts at the end of the day, right?
Anyhoo, next time....better exposure, or maybe all it needs is the blur off.
Agreed with the others, I think its a bit blown out and without the thread title, might not have been seen as a maternity shot, perhaps more of an angle next time to show the focus of the photo on the pregnancy, than the hands.