Puppies shouldn't leave Mom until they're at least eight weeks of age, and there are actually some good reasons why veterinarians recommend this.
Dogs, just like people, develop social skills as babies. Puppies pick up some critical information during those first two months, from interactions with their littermates and with their mother. They learn appropriate responses and boundaries in play. It makes for easier to train and more socialable dog in most instances.
Another reason is the overall health of the dog. At eight weeks of age, our puppies have, through the course of nursing, acquired whats called "maternally derived antibodies". This is a fancy way of saying they've obtained superior immune systems and immune responses to some common infectious diseases through a substance in Mom's milk called colostrum. It's more likely that they'll respond well to vaccinations after they're sent off to their new homes.
