Sentence:  You have two flights of stairs and no elevator. As you get closer to your due date that will be awkward, and once the baby arrives a <WSD>pusher</WSD> would never make it up there. You can hardly carry a fully loaded pram and baby up two flights. 
Meaning of the word marked with <WSD> tags:  A device that one pushes in order to transport a baby while on foot, such as a stroller or pram (as opposed to a carrier such as a front or back pack).