Cleft palates occur when the bones and other tissue inside the upper jaw fail to close properly during development, leaving an opening between the mouth and the nasal passages. The size of the cleft can vary from, an opening in the roof of the mouth to a gap that divides the gum and underlying bone in the upper jaw and even up to the nostrils. The most severe forms will be readily visible. Those which are confined to the inside of the mouth may not be so obvious but all cleft palates interfere with nursing because the puppy can’t get suction due to the cleft and may even get aspiration pneumonia by breathing milk into the lungs.
Cleft palates may be due to accidents of development or caused by toxic exposure prior to birth. In the 1980s and 1990s there was an x-linked syndrome of multiple skeletal defects that included cleft palate, but this was only in one isolated family of dogs and is unlikely to be present in the breed any longer.