I'm always thinking about that. I don't have a baby yet but planning on having one soon. My yorkie is jealous too.
I can't give you an advice from my experience, but I think that an important way of reducing or avoiding jealously is by giving the yorkie lots of attention. Of course taking care of the baby requires much time, but you have try not to make him feel like the baby is stealing you from him. It's like when you have siblings, and they are jealous of each other. Yorkies are furbabies, they are not just dogs, they deserve our attention. Someone said that each time you give birth to a child your love gets multiplied not divided. So multiply your love and attention towards both and you should be fine
