Total 100% myth, by spaying your dog BEFORE their first cycle you are taking away so many illnesses that can crop up and can all be prevented by a simple spay. And in all honesty, its much cheaper to spay, cancer costs a fortune to treat, if a bitch has trouble whelping that c-section will also cost money, it may cost her life etc etc...Not saying you are wanting to breed, but it does happen, males can smell a dog in season from pretty far away. They have been known to jump fences, rape a bitch on a wlk with her owner, get nasty etc etc...Its uncomfortable for them to be in heat.