What causes a puppy to be born small, not gain weight, and die?

Cleft palates sealing up on their own is a new one on me. I've never raised puppies but know that cleft palate kittens don't survive without surgery, and rarely then. They have to be tube-fed, not bottle-fed, until large enough for surgery. If they nurse or suck on a bottle, the milk gets into their tracheas, then lungs, causing fatal pneumonia.