Does a baby's sleeping position affect the development of motor skills? In one study, published in the Archives of Pediatric Adolescent Medicine, 343 full-term infants were examined at their 4-month checkups for various developmental milestones, such as rolling over, grasping a rattle, reaching for an object, and so on. The baby's predominant sleep position-either prone (on the stomach) or supine (on the back) or side-was determined by a telephone interview with the parent. The sample results for 320 of the 343 infants for whom information was received are shown here:

The researcher reported that infants who slept in the side or supine position were less likely to roll over at the 4-month checkup than infants who slept primarily in the prone position (P

Number of Infants Number That Roli Over Prone 121 93 Supine or Side 199 119