actually DAN, there is proof that females who are spayed are MUCH less likley to get mammary tumors and cannot get ovarian cycsts and cancers (which belive me...are no fun and absolutly deadly as they usually dont show any symptoms) spaying also = no payometra, (which can also be deadly) and of course removes all risk of a femal dying during complications of whelping...
in MALES theres limited health benefits, but in females those benefits are huge...
you will notice testicular cancer in an intact male, the testicles will swell and discolor...but ovarian cancer (which almost killed me btw) is not a "visible" cancer, very rarely does it show physical sighns beyond painfull periods, difficulty getting pregnant and abdominal pain... and since dogs cant speak, how will you know if shes cramping?!
spaying will also remove the messy aspect of having an intact dog, your female will no longer bleed or have mood swings which come along with her heat (or period).
it does however also mean she will not be able to have puppies, meaning not only would she not be able to have puppies if you tried to breed her on purpose but also means you dont have to worry about stray male dogs comming into your garden or sitting outside your house, you dont have to worry about her trying to get out to go and see them.
PLEASE PLEASE PLEASE get your dog spayed, she should NOT have puppies, and spaying her is the only surefire way to prevent it.