Final answer:
The most important advice for new parents to prevent SIDS is to always place their infant in a supine sleeping position. This practice is paramount among recommendations for reducing the risk of SIDS.
Step-by-step explanation:
When teaching new parents prevention of sudden infant death syndrome (SIDS), the most important practice a nurse should instruct them to do is C. Place the infant in a supine position for sleep. This is because sleeping on the back has been strongly associated with a decreased risk of SIDS. The supine position is recommended, avoiding soft bedding, pillows, and crib bumpers that could pose suffocation risks. Additionally, to further reduce the risk of SIDS, parents should avoid overheating the infant and ensure that no one smokes in the home. While home monitoring systems may provide some level of reassurance to parents, they are not recommended as a primary strategy to prevent SIDS, and following the recommended immunization schedule, though important for overall health, is not the single most important practice specifically for the prevention of SIDS.