The most common reason to pump is to collect your milk so your baby can have it when you're not around, and to maintain your milk supply for when you're together. This is essential if you're going back to work but want to continue nursing.
Pumping also means you don't have to be on call for every feeding when you're at home. Your partner (or another helper) can feed your baby your milk from a bottle allowing you to get more uninterrupted sleep or take a break from baby care. (Letting Dad take over some of the feedings also helps him bond with the baby!)
You may also use a breast pump to stimulate your milk production and increase your supply, to collect milk to feed a premature baby or one who can't latch on to your breast, or to relieve the pain and pressure of engorged breasts. Some moms exclusively pump, feeding their babies expressed milk in a bottle instead of nursing.
Finally, pumping allows you to keep your milk supply up if your practitioner advises you to stop nursing temporarily because you're taking medications that might be harmful to your baby, for example, or if you're hospitalized for a short time and can't breastfeed throughout the day.
Most women express their milk using an electric or manual pump. (Some women prefer to express their milk by hand, but most feel that using a pump is faster and easier.) Although it may feel strange at first to use a machine to get milk from your breasts, it usually doesn't take long for the process to become quick and easy.
Choosing the breast pump that's right for you depends on how often you plan to use one and how much time you can devote to pumping. If you work full time and have to find time to pump during a busy workday, you'll want to use an electric model that allows you to pump both breasts at the same time. But if you only need to pump a few ounces occasionally so your partner can feed the baby while you're out for a short while, an inexpensive manual pump may do just fine.
It's best to put breast milk in plastic or glass feeding bottles with secure caps to seal in freshness. You can also use plastic bags made especially for storing milk or disposable baby bottle liners. Remember to write the date on the bottle or bag before putting it in the refrigerator or freezer so you'll know when you pumped it. You may be surprised to see what breast milk looks like. It's normal for the fat to separate and float to the top, and sometimes the milk has a bluish hue.
Use fresh, refrigerated milk within 72 hours. Milk can last at least three months in the freezer of a double-door fridge or three to six months if you have it in a stand-alone freezer set no higher than 0 degrees Fahrenheit. Once you've thawed frozen milk, you can keep it in the refrigerator for up to 24 hours. (If you haven't used it in that time, you'll have to throw it away, since you can't refreeze it.)
To thaw frozen milk, place the bottle or bag in a bowl of warm water and run it under warm tap water, or defrost it in the refrigerator overnight. Don't use the microwave for defrosting or warming because this damages the nutrients in breast milk.
Most experts recommend throwing out any milk that's left in your baby's bottle after a feeding, though some may tell you it's okay to save a partial bottle of breast milk for up to an hour at room temperature (if your baby falls asleep then wakes up to finish the feeding, for instance).