The American Academy of Pediatrics and the U.S. Consumer Product Safety Commission recommend placing a newborn in a crib and not co-sleeping with the parents for safety reasons. Newborns average about 16 hours of sleep a day at a span of three to four hours at a time. This is when the baby is at his most vulnerable stage so caution should apply when positioning the springs on a crib. The placement of the springs should be at its highest for a newborn to allow easy access for parents.
At 4 to 7 months, the infant most likely will start to crawl and pull himself up. He will be accustomed to changing positions quickly and more often. However, it will be a few more months until the infant can start walking. At this time, it is safe to place the springs on the middle rungs of the crib. Make sure the baby sleeps with the rail up at this stage.
When a baby reaches 8 months old, he might begin to move around the area of a room by holding on to the furniture. Infants usually start taking their first steps independently when they turn 1. This is when the springs of the crib should be at their lowest. This will keep the baby from grabbing onto the rail to pull himself up to stand, which can cause him to fall out.
Check the springs frequently to ensure the hooks that attach the springs to the brackets on the crib legs have not come loose. At the same time, check the brackets to make sure they are still properly attached to the crib legs.