This article by a maltese breeder explains it perfectly and applies to our breed as well ...
Why is there a 12-week-old rule about selling a Maltese puppy? Have you ever wondered why it is fine to place a large breed puppy at 8 weeks old as opposed to a small breed puppy? Why does the American Maltese Association code of ethics require a Maltese puppy be 12 weeks of age before they are placed in homes? There are many reasons!! I am going to compare lab puppies to Maltese puppies because I have had experience with both breeds in hopes of making it more easily understandable as to why this "12-week-old" rule exists for Maltese and many other "toy" breeds.
At birth there is not a lot of difference between Maltese puppies and lab puppies.......both litters depend on their moms for food, comfort, and heat. Shortly there after the differences start to become very apparent. A litter of three week old lab puppies are up playing and maneuvering around pretty well and are usually 3 pounds or more in weight. They are also getting their teeth and starting to eat gruel. A litter of Maltese puppies at three weeks of age have an average weight of 13.5 ounces and are just barely starting to get up on their legs and maneuver around readily....they have very little coordination at this point.
By four weeks old a lab litter is usually weaned from their mom. Maltese puppies at 4 weeks old are still very dependant on their mom's for nourishment although at this point I have moved the water bowl down for them to lap and they do lick at mom's food.
By eight weeks there is a drastic difference between a litter of lab puppies and a litter of Maltese puppies. Eight week old lab puppies usually have their teeth now and are eating puppy food. They are also much larger at this point with an average weight of between 20 to 25 pounds. They also seem to be mentally more mature at this point to me and are able to go to their new homes. In many cases, my Maltese puppies do not even have teeth and are still nursing their moms at eight weeks old.
At eight weeks old my Maltese puppies whose "average" weight is 1 pound 9 ounces usually start to get teeth and when those tiny needle sharp teeth start to come in is when Mom decides it is time to wean. This is a very important and scary time for Maltese puppies. They are used to having a milk bar provided for them and many do not really want to eat that nasty old gruel. Since a Maltese puppy is still very small, normally less than 2 pounds, they are also in danger of getting hypoglycemia which is caused by them not eating enough. This can be a very dangerous time for a Maltese puppy since hypoglycemia can result in seizures and even death if not taken care of immediately. This is also the normal time when a Maltese puppy starts to learn about puppy etiquette from it's mom and any other adults around and from playing with siblings, if there is more than one puppy in the litter. They learn about appropriate doggy behavior at this point. This is very important for the future well being and mental stability of this Maltese puppy. Maltese puppies learn some valuable lessons in the weeks after weaning, including how to get along with other dogs, and that biting hurts. These are lessons, all learned in puppy play, that no dog should be without. Some of the most important lessons in life, a puppy will learn from it's mom and siblings. They NEED this time with their mom and littermates!!
An eight week old Maltese puppy may or may not be ready for it's first puppy shot. Resent studies on vaccination have proven that vaccinations given to a nursing puppy are basically worthless. They need to be weaned for that vaccination to do what it is supposed to do. My Maltese puppies are usually just receiving their first puppy shot sometime between 8 and 10 weeks old.
Below are pictures of RÍve, Foxstone's Daydream Keeper, at 8 weeks old and at 12 weeks old. You will note that there is not a lot of difference between an eight week old Maltese puppy and a 12 week old Maltese puppy.
(the pictures didn't copy - go to the website link above to see the pics)
She is still a little fluff ball but at 12 weeks old she is better prepared both physically and mentally to go out and face the world.
So if you are looking for a well rounded Maltese puppy that is going to easily adapt into your life style and home with the least amount of problems, that Maltese puppy should be at least 12 weeks old when you bring it into your home....no exceptions!!!!
If a person/breeder is trying to sell you a Maltese puppy that is under 12 weeks old, or heaven forbid, a Maltese puppy that is 8 weeks old or younger, that person is either extremely unknowledgeable of the Maltese breed as a whole or that person does not have the best interests of their Maltese puppies at heart. Either way, in my opinion, you should steer clear of a person, such as this, since they are considered to be, in my opinion, unethical and/or disreputable Maltese breeders.
No "reputable" Maltese breeder is going to sell you a Maltese puppy that is under 12 weeks old!!!!