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.
When is it safe to let my baby sleep on his tummy? To reduce the risk of sudden infant death syndrome (SIDS), experts recommend that you place your baby on his back when you put him down to sleep during his first year. The risk of SIDS peaks between 1 and 4 months of age but remains a threat until babies are 12 months. Once your baby is strong enough to roll from back to front and front to back by himself, you don't need to worry about him rolling onto his stomach during sleep.