Don't use baby "sleep positioners."

The FDA and the CPSC report that 12 infants between the ages of 1 month and 4 four months have died when they suffocated in sleep positioners or became trapped and suffocated between a sleep positioner and the side of a crib or bassinet. Most of the infants suffocated after rolling from a side to stomach position. In addition to the reported deaths, the U.S. Consumer Product Safety Commission has received dozens of reports of infants who were placed on their backs or sides in sleep positioners, only to be found later in potentially hazardous positions within or next to the sleep positioners.
Sleep positioners typically claim to do one or all of the following: aid in food digestion to ease colic or the symptoms of gastroesophageal reflux disease (GERD); and prevent flat head syndrome (plagiocephaly). In light of the new safety data, FDA believes any benefit from using these devices to ease GERD or prevent plagiocephaly is outweighed by the risk of suffocation.