A breeder could probably offer you the best advice, but maybe I can try to offer my input too...
Your baby is small, and if she were mine, I would be worried sick through the pregnancy. There are lots of possible problems with deliveries in yorkies, especially small ones, and then, even if the babies were born without a hitch, I'd have to worry about taking care of a tiny litter of babies too. I know you're a wonderful mom, so I think when you consider the dangers to your beautiful yorkie, and all the concern involved, you'll decide that its not worth the worry.
