However, the book has undergone substantial revision over the years because some of the advice it gave was contentious, if not downright harmful. Early editions, for example, recommended lying babies face down to sleep. We now know that this is a contributory factor in [[Sudden Infant Death Syndrome]] (SIDS, or Cot Death) and that babies should be placed on their back. | However, the book has undergone substantial revision over the years because some of the advice it gave was contentious, if not downright harmful. Early editions, for example, recommended lying babies face down to sleep. We now know that this is a contributory factor in [[Sudden Infant Death Syndrome]] (SIDS, or Cot Death) and that babies should be placed on their back. |