If you want to collect your milk so it can be used for a supplemental feeding later, you need to learn how to express it. You can express your milk either by hand (manually) or by pump (mechanically).

The best time to express your milk is when your breasts are full and you are unable to feed, or when your baby has not completely emptied the breasts after a feeding.

Preparing to express your milk
To prepare to express your milk either manually or mechanically, first wash your hands and make sure any container or equipment (eg, bottle, cup, pump) you are using to collect your milk is sterile. (Follow manufacturer's instructions on cleaning or sterilizing pumps.)

Make sure you are relaxed and comfortable. Some women find it helpful to drink liquids, listen to music, think about the baby, or look at a picture of the baby before expressing their milk to encourage the "let-down" reflex. This reflex is initiated by the suckling infant and triggers the milk to be released from the breast.

Massaging your breasts before expression will encourage the "let-down" reflex. To massage, start at the top of the breast. Press firmly with fingers into the chest wall. Move fingers in a circular motion over one spot.

After a few seconds, move fingers to the next spot. Spiral around the breast in this manner, massaging each area.

Then, with your fingertips, lightly stroke from the top of the breast towards the nipple, using a tickle-like stroke. Continue stroking from the periphery to the center around the whole breast.

Manual expression
Place your thumb about 4 cm above the nipple, and the first 2 fingers 4 cm beneath it. Gently push straight in toward your chest wall, then firmly but gently roll your thumb and fingers forward. This action of pushing back and then rolling forward in a rhythmic fashion helps release milk from the ducts and sinuses inside the breast.

Rotate around your breast, using both hands on each breast, to express all sinuses. To avoid damaging sensitive breast tissue, do not squeeze the breast, slide fingers on the skin, or pull the nipple.

Expressing both breasts by hand can take as long as 30 minutes, so don't be frustrated if it takes even more time at first. With practice, it should become easier.

When the stream of milk from the breast diminishes to droplets, you should switch to the other breast. Follow the same instructions with the second breast. You may need to move back and forth from breast to breast, and may need to repeat the massage steps to release as much of your milk as possible.

Mechanical expression
If you use a breast pump to express your milk, be sure to read and follow the manufacturer's instructions carefully before you use it. The pump should be cleaned thoroughly before and after use—or sterilized if recommended by the manufacturer.

To get started, moisten the inside of the pump shield (the part you apply to your breast) with warm water. Place the pump shield against your breast so that the nipple is centered within the inner opening of the shield. You may find it easier if you lean in toward the pump to make a good seal between your breast and the shield.

If the pump is not automatic, push and pull the pump's cylinder to create a flow of milk from your breast. Additional breast massage while you pump can help the milk flow.

Mechanical expression may take as long as 20 minutes. When the flow decreases to droplets, carefully break the seal, wipe your breast with a clean, dry cloth, and follow the same procedure with the second breast. As with manual expression, you may find that you need to go back and forth from breast to breast until both are emptied.

Storage
Your milk should be stored in a very clean (preferably sterile) container. Small plastic baby bottles, disposable plastic bottle liners, or durable plastic bags work well. Be sure to label the container with the date or time of collection for future reference.

Refrigerated milk should be used within 48 hours. Remove from the refrigerator just before using. Warm the milk to room temperature by running under warm water or placing it in a container of warm water for 5 to 10 minutes. It should not be warmed in a microwave oven or on a stove.

Breast milk can also be stored in a freezer for 3 months. It may be thawed in the refrigerator—where it can stay for up to 24 hours—or in warm water. It should not be defrosted in a microwave oven or on a stove. Breast milk should not be refrozen.