asÂ·soÂ·ciÂ·aÂ·tive property. The property of addition and multiplication which states that a difference in the grouping of numbers being added or multiplied will not change the result, as long as the order of the numbers stays the same. For example, 3 + (4 + 5) is equal to (3 + 4) + 5. See also commutative property, distributive property. 1  Facebook.
The most common recommendation is to initially place infants to sleep on their backs for the first 12 months. However, when the infant is able to roll over on their own in to the sleep position of his/her choice than it is fine to leave the baby in that position. My children are now 29, 27, 24, and 11.
So the reason for the Back to Sleep issue is that it has shown to decrease the rate of SIDS (Sudden Infant Death Syndrome). A baby can start sleeping on there tummy when they are able to roll over, typically 3-4 months of age.Typically start on the back and if they roll....then they roll. A baby can have some tummy time (around 5-15 minutes) supervised around 1-2 months of age when the baby is able to hold up their head.ou are doing the right thing! Never allow them to sleep on their tummy unless you are watching them until they are 1 year old or more. SIDS is a serious concern and the risk increases when the baby reaches 4 months and starts to be able to roll over.