I think your puppy and 15 month old will love each other.  You will want to watch them closely while together and never leave them unattended.  Once they get to know each other I think they will be great playmates.  Your Yorkie will probably even keep an eye out for the baby.  I babysit two young children ages 4 and 10 months old.  My Yorkie was just curious about the baby more than anything.  My own kids are 10 and 11 yrs old and and he loves them.  They have the energy he craves!  Getting your Yorkie as a puppy raised with children he won't know any different.  Enjoy your new furbaby! Congratulations
