Use the straight wide mouthed bottles with a screwed top. The old boat shaped bottle has too narrow a mouth for proper cleaning and it is also difficult to measure the milk. The screw top allows air to flow in as the baby drinks and prevents a vacuum from forming. If you find that air bubbles are not entering the bottle as the baby drinks, loosen the screw top a little.
It is simpler to have three or four bottles that can be sterilised together and can be ready for use than to sterilise one bottle at each feed. You will only need a large enough container to boil all the bottles together. any cooking utensil with a lid will do. wash the bottles with soap and water with the help of a bottle brush immediately after use and keep aside for sterilising.
For sterilising place the bottles along with the nipples and screw tops in the container, add cold water and put it on to boil. Allow it t o boil hard for at least five minutes. Then pour off the water and keep the container covered. When taking off the bottles and nipples, only touch the outside of the bottle and the screw tops so that there is no contamination.
Most nipples come ready with holes, but you must test them to see if they are the correct size. if the hole is too small, and this is particularly relevant to small babies, the baby will fall asleep before he or she has had enough milk. On the other hand, if the nipple hole is too large, you will find that the baby chokes and struggles during his feed and while he will get enough milk, he will not get enough of sucking. These babies often tend to start sucking their thumbs by the age of four to five months to satisfy their desire for sucking. So make sure that the nipple hole is just right.
To test it, invert the bottle, the milk should first come out in a fine spray for a second or two and then it drops.