Remember to put a bumper guard around the perimeter of the whelping box so that she does not inadvertantly crush a pup between her back and the wall of the box. Just remember that if it becomes necessary to cut an umbilical cord use something dull so that it actually crushes the cord--just as Redyre has indicated. The minimum size whelping box that I use for my beagles is2' by 3.5'. I also provide heat from beneath and above.