"Inclined position" refers to the orientation or arrangement of something in a tilted or slanted manner, rather than being flat or upright. Full definition
While babies who are about a more than a couple of months old will prefer a less inclined position. (babyambition.com)
This Fisher - Price product allows your newborn to lie flat or in proper inclining positions with comforting vibrations. (followmum.com)
You understand that a newborn can not support its head yet and will require that incline position compete with head support for them to be comfortable until the moment they can sit upright without support. (thankyourbaby.com)