a 12 pound dog pregnant by a 45 lb dog ? Oh man - PLEASE stay on top of that - I would have terminated that one too as Kristy said -
and your vet should be advising you on how to handle this -
I don't think your girl can or should deliver these puppies...the puppies may be way bigger than she can handle and she will need probably need a C section for sure. I'd be worried if it were my female.
everyone is right - IF you spay her and neuter him and you won't have to worry about this again. I hope she'll be ok - poor girl !!
Good luck !!