Shrink wrap is when during hatching, the inner membrane dries out and shrinks around the chick. It restricts there movement and makes natural hatching impossible. Most attribute it to too low of humidity at hatch. I think that is one cause, but not the only cause since I had shrink wrap of 5 broody hatched eggs when it was raining, no drying fan to blow on them and couldn't have gotten higher humidity then a rainy couple of days.