So if a 10 year old girl gets pregnant and has a baby successfully, then that's okay too?
Sure, as long as a 6 month old dog goes into heat and gets pregnant first go around, that's ok... 6 month old cat, sure...
When animals get gravid/pregnant what have you, too early, it's detrimental to their growth and can stunt them. I've had it happen in rats and have seen it happen alot when breeders breed them at 3-4 months old when the animal isn't even done growing.