Sounds more like a fault with the settings of the printer driver.
Well sometimes if you have things a bit close to the margins of the printable area, which is often the case with labels, a printer driver will automatically shrink the page to fit within the printable area. But of course if you have a very precise full-page design where the printable area has been taken into account in your design in any case, you want the printer to ignore the fact that part of the design is outside the printable area and print the design at 100% regardless.
You need to make sure the driver is printing at 100% and ignoring the fact that some blank or white graphic objects may lay outside the printable area.
So I doubt if it's a problem with Word. I would suspect the printer settings myself :)