The phrase "sucking movements" refers to the actions or motions made when someone sucks on something, like a baby sucking on a bottle or your lips making a sucking motion when drinking through a straw. Full definition
Loss or reduction of milk supply due to incorrect sucking movements occurs often, so that bottle feeding may be introduced earlier than planned. (tonguetie.net)
Signs of hunger include rooting or looking for a nipple, opening and closing the mouth, sticking out the tongue, sucking on hands or fingers and making sucking movements with the mouth, according to the KidsHealth website. (howtoadult.com)
They will be doing lots of practise sucking movements ready to latch on for that first post-birth feed, and will be starting to move further down your pelvis ready for D - day. (bounty.com)