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.
For the first three weeks of my 5-week-old's life, he hardly slept. I'd put him on his back and his startle reflex would wake him up. What a nightmare! One day I put him on his stomach and he slept for four hours -- so now he naps on his tummy while I keep an eye on him. At night, he'll only sleep on his back if he's in bed with me. I want to put him in his crib, but not on his tummy because I'm afraid of SIDS. Please help!