i stopped wearing underwired bras in the middle of the second tri, mainly beacsue when i was sat in the car for ages the wire was digging into my bump
noraml non wired or even a decent sports bra will do though, there is no need to be 'sold' into buying maternity bras as they really done do anything different to an underwired bra, much later if you are breastfeeding then you will need to look into getting nursing bras, but no point buying them till you are about to have the lo anyway coz boobs will change a lot
i never buy nursing bras until about 2 weeks after baby arrives, that way boobs have settled