I first discovered Ventaire bottles when my daughter, who is now 7, was a baby.  She was lactose intolerant and spit up quite frequently.  The design of these bottles allowed for the excess air inside the bottle to escape, preventing spit up.  I also used these when I had my son.  He was diagnosed with GERDS (gastro-esophogeal reflux disease).  The bottles are a bit pricey, but worth every penny to me :) I love these bottles!