The summary below has been based on information provided by the manufacture of the Dr Brown’s Fully Vented bottle in the USA - some of the information you may already be familiar with.

As the Dr Brown's bottle is fully-vented, it allows positive-pressure flow, similar to breastfeeding. This is essential for the baby to feed without having to suck against a vacuum, may help with wind, colic, discourages ear infections and preserves the vitamins in the formula or liquid. However, at times, milk or formula can exit the bottle through the vent if the bottle is not handled or used properly. Slight errors can occasionally cause milk to leak out the vent, or a slight symmetry or fitting issue with the internal vents when placed inside.

1) Do Not Overfill the Bottles
Do not exceed the fill-line of the bottles otherwise the extra liquid may escape into the vent and then exit out the two vent holes on the side under the collar. To note, if you use formula, make sure the combination of powder and water does not exceed the Fill line.

2) Do not Heat the Milk With the Vent in Place
As milk is heated it expands. If you keep the Dr Brown’s vent in place as you heat milk or formula, the liquid will be forced up into the vent and cause leaking. To avoid this problem, either heat your bottles without the vent in or loosen the teat collar after heating the milk so that the pressure can equalize and the milk can leave the vent. Then re-tighten the collar.If you place the Internal vent into milk that is overheated, the milk may rise and condense inside of the vent. Therefore always wait until the milk is cool enough for your baby to actually use before placing the vent inside.

3) Do Not Shake the Bottle With the Vent Inserted
If you shake your bottles to mix formula while you still have the vent inserted, you are likely causing liquid to enter the vent and leak out later. There are a couple ways to avoid this problem. Mix the baby formula by stirring the liquid instead of shaking it. This has the added benefit of reducing air bubbles which may future reduce infant wind and colic. If you prefer shaking your bottles, use the Dr Brown’s Storage Caps. Shake with the cap in place, and when the formula is properly mixed you can remove the cap and insert the full vent. It is best to wait for the air bubbles to subside as well.

4) Do not Submerge the Reservoir Tube
When feeding your baby, avoid keeping the bottle perfectly level. Avoid submerging the reservoir tube under liquid as you feed your infant. as you might end up with some leakage. The ideal angle is 45 degrees during feeding. This should keep the end of the tube out of the the liquid. If liquid does end up inside the reservoir tube, all you need to do is stop the feeding, turn the bottle upright, and loosen the teat collar a bit to release the built-up pressure. The milk should then fall back into place at the bottom of the bottle, and you can then re-tighten the collar and resume feeding.

5) Do not Over-Tighten or Under-Tighten the Teat Collar
Both over-tightening or under-tightening the Teat collar can cause leakage. Over-tightening causes too much pressure to build up, and under-tightening the collar doesn't allow the bottle to form the seal that holds back the liquid during feeding. A suggestion would be to twist the collar onto the bottle until you feel a small amount of resistance, then give it one more half-turn.

6) Use an Age-Appropriate Teat
If your baby is sucking on the teat too hard, the baby could cause the teat seal to break. If this happens to you, you likely to need to move up to a faster-flow Teat. On the other hand, if your baby tries to block the flow or slow down the milk, the infant can cause fluid to be forced backward into the vent. If that happens to you, then you probably need to move to a slower-flow teat.

7) If you are using a Bottle Warmer (or standing the bottle in boiling water) to heat up, you may need to open and close the bottle top a few times to release the pressure inside the bottle. During warming, the liquid expands and creates pressure which will cause the milk to travel up the vent tube, where it may leak out of the side vent holes and collar. Warming the bottle without the vent system or cap on, may prevent leaking.

8) If you are placing the bottle in a travel bag - make sure to use Travel Caps to close the bottle. This will avoid the liquid possibly exiting the two vent holes on the side of the bottle should the bottle build up pressure from warm liquid , or if the bottle falls to the side or on an angle while traveling.

9) If leaking is coming from the top of the teat hole - please note: Dr Brown’s bottles feature an open venting system which allows milk to flow freely from the teat hole. We suggest keeping the bottle upright at all times when not is use, and using a flat screw-on travel cap when transporting the bottle.