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.
Rule: Put your baby to sleep on her back. To help prevent SIDS, the American Academy of Pediatrics (AAP) recommends putting your child to sleep on her back until she's a year old. If your baby can flip over before that, you don't have to go in her room to turn her onto her back. But you should still wait a year before actually putting her down in her crib on her tummy. Rule: Support your infant's head