Pumping Breast Milk 101

Written by: Sabrina Granniss, IBCLC

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Time to read 8 min

Many mothers pump breast milk for their babies at some point during their breastfeeding journey. There are a variety of reasons for pumping milk, including helping with the establishment of the milk supply when there are challenges in the beginning, increasing the milk supply, having milk to leave for your baby while away, or working, exclusively pumping your milk to provide for your baby, or to build a small “just in case” stash. Pumping looks different for everyone, depending on the reason for pumping and their baby’s needs.

Making Milk

During pregnancy, the breasts undergo changes to produce and store milk for the newborn baby. Colostrum begins to be produced as early as 12-16 weeks during pregnancy and may begin to leak in the 3rd trimester. (1)  As estrogen increases, milk ducts are developed, and the secretion of prolactin is signaled. Higher progesterone levels are responsible for milk-making cells to form and grow. 


Breast changes in pregnancy:


  • The breasts may be a little sore or sensitive 
  • Breasts feel heavier and swollen  
  • Areola and nipple appear darker
  • Montgomery Tubercles develop on the areola
  • Veining in the breast is more visible due to increased blood flow
  • Ache in the armpit area - breast tissue extends into this area and is called Tail Of Spence

After your baby is born, the placenta is delivered, causing progesterone and estrogen to drop. This drop signals Prolactin, the hormone responsible for making milk, to increase and for milk production to increase. Over the next 2-3 days, your milk will transition from colostrum to mature milk. Colostrum is very concentrated compared to mature milk, which is abundant in volume. 


Keep your baby skin-to-skin, beginning within the first hour after birth, and offer the breast often. Hormones drive this stage of lactation. Milk will be made even if milk is not being removed. How often your baby nurses and how much milk is removed each feeding is essential during this stage. When milk is removed, prolactin signals for more milk to be made. If the breast remains full of milk, it signals to slow down milk production. Feeding your newborn often means more times milk is removed and more refilling of milk occurs. If your baby goes to the breast frequently but is not removing sufficient milk, production is also affected. Without adequate and frequent milk removal, some of the cells that hold milk will begin to shut down. (2) Around 10 days postpartum, milk supply begins to be driven by demand.  

When to start pumping breastmilk

Not all parents need to pump. You don't need to include pumping if you will be with your baby for every feeding. 

  • If possible, wait to begin pumping until 4-6 weeks postpartum when your milk supply is well established, and you are making the amount of milk needed for your baby to grow and thrive. 
  • You’ll want to begin pumping 2-3 weeks before returning to work. Suppose you need to start pumping early for a return to work. In that case, scheduling a returning-to-work consult with your IBCLC (International Board Certified Lactation Consultant) may be beneficial to help navigate pumping.

Pumping oversupply

Beginning to pump too soon can signal higher milk production and lead to an oversupply. You are meant to produce the amount of milk needed for your baby. Having too much milk can make you and your baby uncomfortable.

Oversupply symptoms

  • Plugged ducts
  • Mastitis
  • Painful breasts 
  • Difficulty latching
  • Choking and gagging during the letdown
  • Gassiness
  • Gulping during feeding
  • Resisting the breast
  • Too much or too little weight gain

When to start pumping breastmilk

How often you will be away from your baby will determine your pumping and milk-storing needs. 


Occasional separations:


  1. You can use a silicone pump after your baby has nursed from both breasts. Your baby will nurse from breast #1, and then as they are nursing breast #2, you can have the silicone breast pump 
  2. on Side #1 to collect milk to store. You can combine fresh milk with refrigerated milk following proper storage guidelines. (3) Only collect as much as you need to store for your baby to avoid creating an oversupply.
  3. Add one regular pumping session daily. Pump ½-1 hour after your baby nurses with an electric breast pump for a small milk stash. Choose one time of day, typically the morning, when milk production is higher, and pump each day around the same time to store 2-4 ounces daily. Alternate which breast you pump each day. This method will gradually increase the milk supply to accommodate the one pumping session per day without causing an oversupply.
  4. Hand expression is another effective option to remove milk. Some lactating folks get more milk from hand expression than from a pump. Benefits include no extra tools needed and always being available.

Returning to work

Milk production remains fairly constant from about 6 weeks until the introduction of solid foods. Your baby eats about 24- 30 oz per 24 hours, taking 2 - 4 oz per feeding. (4) Most parents like to store enough milk for 2 days away from the baby to have a little cushion of extra milk.


A double electric pump is often the most effective way to collect milk if you need to pump for returning to work. Many options are available, including hands-free collection cups to make pumping more convenient when your hands need to be free or taking a break at work is challenging.


The Legendairy Milk Duette is a dual electric breast pump with a variety of individual speeds and suction levels for each breast to customize your pumping experience.


To determine how much milk you need to pump and leave for your baby while you are away from them, estimate how many times your baby nurses in 24 hours and divide that by the average amount of milk they drink daily, which varies between 24 - 30 ounces. You can use 25 ounces as an average. This will give you the amount per bottle. Plan on one bottle every 2-3 hours while away.

Example: 25 ounces divided by 10 feeds per 24 hours = 2.5 ounces

Example: 30 ounces divided by 10 feeds per 24 hours = 3 ounces


The amount of milk you are able to pump is dependent on how old your baby is, what time of day you pump, when you last nursed or pumped, and your breast storage capacity. 

  • Most people make more milk in the morning, making it an excellent time to pump 
  • Wait 30 - 60 minutes since the last milk removal

The average amount to expect from pumping during a regular pumping session is 3 - 4 ounces. (6) If you are pumping between feeds, the amount may be closer to 1.5 - 2 ounces. 

Pumping Tips

Pump Parts

Ensure all your pump parts are working properly. Some parts will need to be replaced more frequently than others. How often you replace them depends on how often you are pumping. The guidelines below are based on pumping 3 or more times a day and less than 3 times per day. The more often you pump, the sooner the parts will wear out.


  • Duckbills every 1-3 months
  • Valve membranes every 2 weeks - 2 months
  • Backflow protectors every 3 - 6 months
  • Shield/flange - as needed
  • Tubing - as needed

Flange Fit 


Pumping should be comfortable and never hurt. If a flange is too big or small, it can be uncomfortable and cause damage to the nipple and areola. If the shield/flange is the wrong size, it will not be as effective at removing milk and can affect your milk supply over time. If you’re taking the time to pump, you want to get the most milk possible. 


Flange/shield size can change over the course of nursing. A nipple ruler can be a helpful tool for finding your correct flange size. Many IBCLCs (International Board Certified Lactation Consultants) offer Flange Fitting Consults.


Using a lubricant on your breast shield/flange, like Legendairy Milk Pumping Spray , can add comfort while pumping, and the oils nourish your skin.


Expressing Your Milk


It can take time and practice pumping for your body to respond to the pump. It is common not to see immediate results. 


Here are some techniques that can help:


  • Hands-on pumping - always use gentle touch!
  • Add heat - use a warm heat pack to encourage milk flow
  • Breast compressions (5)
  • Relax! Stress inhibits milk flow

Storing Your Milk

  • Always wash your hands and storage containers before pumping and storing your milk
  • Label the storage container with the date (and child’s name if needed)
  • Store 2 - 4 ounces per container. Smaller amounts are better, so milk is not wasted
  • Freshly pumped milk can stay at room temperature for 4 hours (up to 6 - 8 hours)
  • In the back of the refrigerator for 4 days (up to 8 days)
  • In the freezer section of a refrigerator for 9 months
  • In a deep freezer for 12 months

Using Your Stored Milk

Milk quality does degrade the longer it is in the freezer, so it is best only to store what you will need for your baby for a couple of days in most circumstances. (7) Store newly pumped milk in the back of older pumped milk so you grab the older pumped milk to give your baby first. 


  • Thaw milk from the freezer in the fridge overnight
  • Never microwave or heat milk on the stove
  • Warm defrosted milk in a sealed container in a bowl of warm water
  • Always check milk temperature before feeding your baby
  • Shake or stir the milk to avoid hot spots
  • Use thawed milk within 24 hours and room temperature milk within 2 hours
  • Never refreeze thawed milk
  • If milk is leftover after you feed it to your baby, it should be used within 2 hours

Learning about pumping can seem overwhelming at first. Having some basic tips and facts about what to expect can help make it easier. Experimenting is part of the process of finding what works best for you and your baby. Using flanges that fit you best, replacing pump parts as needed, and using hands-on techniques while pumping help you get more milk out at your pump sessions. Remember, your IBCLC is always available if you need a little extra guidance or a plan for making pumping work for you.

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