[Ellie May]

Four months isn't considered too young for a lot of dogs. With the Yorkies, there is no harm in waiting to let them gain weight. Also, spay incontinence is less likely if you hold off. But waiting until after the first heat raises the chances of getting mammary cancer from <1% to 8%. There are some studies that suggest it shouldn't be done before a year, but really every owner (and their vet) needs to look at the science behind the surgery and make an informed decision.