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.
BabyCentre's physiotherapy expert. If you normally sleep on your back, it's safe to continue doing so during the first trimester. But as your womb (uterus) gets heavier in the second trimester, it's best to lie on your side, ideally your left side. After 16 weeks of pregnancy, sleeping on your back isn't such a good idea. That's because your baby is pressing on the vein that returns blood from your lower body to your heart. Of course, we all toss and turn during a night's sleep. So if you wake up on your back, try not to worry.