Designed by a doctor, Dr. Brown’s Natural Flow is the only baby bottle to feature an internal vent system that helps preserve vitamins C, A, & E by minimizing oxidation of breast milk and formula. The bottles also mimic the feeling of breastfeeding, which helps to reduce colic, spit-up, burping and gas by eliminating negative pressure and air bubbles. Every bottle is BPA-free and contains no PVC, lead or phthalates, and many hospitals, NICUs, and doctor offices use Dr Brown’s bottles, a testament to their superior safety and efficacy.