I just read some information that I think just changed my life and I want to know if any other ladies on here have experience with this, and is it true. It said that for playtex ventaire bottles you are not supposed to shake to the bottle to mix the milk either with powder milk or breast milk, you're supposed to mix it in a different container and then pour it into the bottle, because it will trap air and then cause the baby gas. I am wondering if this could also be true of other bottles. I always shake the bottle before I give my baby milk, either breast milk when i warm it up under running water or powdered milk to mix it. My baby spits up a little mostly every time she drinks milk and she's fussy while feeding, now I'm here really thinking it's because I shake the bottle so much and there's so much air in it. I have been using the Phillip avent bottles only, but today someone gave me some playtex ventaire bottles, does it make much of a difference or is it just me shaking it that's a problem?