You asked

When can I start to express breast milk into a bottle?

You can start expressing your milk as soon as your baby is born, but this should be done only if you have a good enough reason to. Babies who are born prematurely and cannot breastfeed for a few days or weeks for example, will need expressed breast milk. It is highly recommended though, that you spend some time learning how to position your baby properly and getting him to latch on correctly so that you do not experience any discomfort during breastfeeding. It must be mentioned that babies are much more adept at getting milk from the breast than you or any pump, manual or electric, will ever be able to.
If you express in the early days following the birth of your baby, you will get very small amounts of milk. This is quite normal, as it takes some time for your milk to be established. However, as you become more used to expressing, the amounts of milk you get will become more and more.
You will need to simulate your baby’s feeding pattern and express at least eight to ten times in a 24-hour period, with one of them being during the night. You should stick to this routine no matter what amount of milk you express each time.
Do note that breastfeeding your baby is not only to give your baby food, but also to enjoy the close intimate relationship involved in the process of breastfeeding. These benefits of breastfeeding last long after the baby has stopped breastfeeding.

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