Make sure that youare choosing a bottle with an anti-colic feature. All NUK bottles feature an innovative Anti-Colic vent system which helps to reduce the risk of infant colic. The valve allows air into the bottle during feeding which prevents an air vacuum and allows baby to feed continuously without swallowing air. In addition, always ensure your baby has a good seal around the nipple to prevent baby from swallowing air from the sides of their mouth.