Many mothers may choose to bottle feed their babies. Some may wish to express their own breast milk to allow someone else to give baby a bottle; some may be advised by their pediatrician to give supplementary bottles and some mothers may simply choose not to breastfeed. Philips Avant bottle feeding products offer more choices for mothers, making it easy to give baby the best, with the flexibility you deserve. The Natural Feeding Bottles are clinically proven to reduce colic*. They also work with baby's natural feeding rhythm to promote healthy, active feeding. * A clinical study showed that at 2 weeks of age, babies fed with an Avent bottle showed a trend to less colic than those fed with a conventional bottle. The naturally shaped nipple, combined with the fact that your baby controls milk flow more like breastfeeding, makes it easier to combine breast and bottle. As your baby feeds, the unique skirt on the Avent nipple flexes to allow air into the bottle, preventing any vacuum build-up. This allows your baby to suckle almost as at the breast. Listen for the gentle whistling sound and watch the air bubbles burst on the surface of the milk. That's your guarantee that the air is being released into the bottle - not into your baby's tummy. The Philips Avent Natural Feeding Bottles are made from polyethersulfone (PES) - a BPA-free plastic.