Yes, using an 8-ounce glass baby bottle for a newborn is completely fine as long as you have the correct flow of nipple on the bottle. Most glass baby bottles include faster flowing nipples so you'll want to use a slow flow nipple with a larger bottle until baby is ready to move up to a different sized nipple. The only downside to using an 8-ounce glass baby bottle is it will be heavier than a 6-ounce bottle.