Even before our child was born we were told that newborns and infants should sleep on a flat mattress. No one, however, told us when to introduce a pillow.
When can and/or should children start sleeping on pillows?
I haven't been able to find anything remotely official (e.g. NIH study), but found this so far:
John Pearce and Jane Bidder, authors of "Baby and Toddler Sleep Program: How to Get Your Child to Sleep," warn parents to wait as long as possible to introduce a pillow, preferably until a toddler reaches 18 months of age or later. (src)
The main reason to delay is the risk of suffocation.
According to AAP (American Academy of Pediatrics), it is still not clear on when it is safe to give a baby her/his own pillow. Even so, some experts seem to agree that the safest time is when your child is one year old. When a child is twelve months old, the risk of suffocation reduces considerably. However, if your child is still sleeping in a crib, remove all objects that may cause suffocation. The pillow should be small, firm and flat like the ones given on airplanes.
Please note that while the source referenced AAP, I wasn't able to find AAP recommendation directly yet.
It they are ok with the crib bed set so there is no need of a pillow for the kids under 2. It will be suffocation for the kids while using it.
If you would like to use the pillow for the LO so you need to wait till they move from the crib to bed. orelse you can use a small pillow while he is still using the crib. So you have to be aware that you should be away from using the feather pillows.