Our anti-colic valve is designed to keep air away from your baby's tummy to reduce colic and discomfort*. As your baby feeds, the valve integrated into the nipple flexes to allow air into the bottle to prevent vacuum build up and vents it towards the back of the bottle. It keeps air away from baby’s tummy to help reduce colic and discomfort. * At 2 weeks of age, babies fed with a Philips Avent bottle showed less colic, and significantly less fussing at night compared to babies fed with another competitor bottle. Nipple design proven to prevent nipple collapse and associated air ingestion and feeding interruptions. Specifications are subject to change without notice. What colic is, and how it affects babies? Colic is caused in part by swallowing air while feeding, which creates discomfort in a baby’s digestive system. Symptoms include crying, fussing, gassiness and spit-up.