I agree with the others that say you should consider waiting. It will give you time and a chance to get your Yorkie boy used to your new baby, because your new baby is going to take a lot of your time, then trying to train a new puppy at the same time might put a lot of undue pressure on you and your yorkie boy will sense that.
If it were me, I would wait until the baby is a few months old at least and then re-assess whether adding another Yorkie at that time is a good idea or not. Only you will know when the time comes
