When to start pumping
If you are planning to return to work or school or will be away from your baby for other reasons, you may want to start pumping a few weeks beforehand. This will give you the chance to practice pumping and will give your baby time to get used to feeding from a bottle.
How often to pump
When away from your baby, try to pump at the same times or as often as your baby is breastfeeding.
This will help remind your body to keep making the amount of milk your baby needs.
How much to pump
Pumping at the same times or as often as your baby normally breastfeeds should help your body make about the amount of milk your baby needs. This amount may differ from baby to baby and can change as babies grow. If you find that you are not able to pump as much milk as your baby wants to eat while you are away, you may want to consider adding another pumping session to increase your milk supply.
Source: CDC
Link: https://www.cdc.gov/nutrition/infantandtoddlernutrition/breastfeeding/pumping-breast-milk.html
