Yorshire

Question
How often does a Yorkshire dog have it's menstrual period?

Answer
Ana,

That depends on the yorkie.  Most dogs go into heat every 6 months or so but small dogs are not the same.  The smaller the dog the longer the period of time is between heats.  A yorkie can go into heat anywhere from 6 months to 18 months depending on the individual dog.  My experience has been that the smaller the dog the less frequent the heat.