Except I am not using it as an insult, but simply by the literal definition:
1. a person born of unmarried parents; an illegitimate child.
Well, I'm not sure how the whole "bastard child" thing really works when you're impregnated by the almighty creator of the universe who holds dominion over all things, so that definition may not even apply depending on your interpretation of things.
Still, bastard even in the literal context has never exactly been a mark of pride if you get my drift. I think it would be better to use some sort of euphemism - let's go with Mary's little miracle. Pun intended.