While I haven't ever seen or heard of a Yorkie going into heat at 5 months old I guess it is possible. What you describe can be a sign that the female is in season but she is so very young. Typically Yorkies don't get their first heat until after 9 months old so I would wonder about your girl. There are other conditions like infections of the uterus or bladder that may could "confuse" your puppy and she might think she was in heat. I would recommend you take her to the vet and get it checked out - just in case.
I would expect most vets would like to have her a little larger to do the spay surgery as well but it would be safe to do now if you would like. Vet procedures are safer now and vets more "skilled" at doing surgeries on small dogs so 5 months would not be too young to have her spayed (I would not spay her while she is in heat -if she is - because there is an increased risk of bleeding if spayed when in heat). There is conflicting information out there about pediatric spays so most people wait until 6-9 months to have the spay done so the vet can remove any retained puppy teeth at the same time.
Good luck
Teresa |