Breastfeeding moms know milk supply is determined by demand. The greater a baby nurses, the more milk is produced. Breast pumps ensure milk secretion will continue any time you can't nurse your childwhen you are at work or otherwise away from your baby. They're also more predictable and convenient to use than using your hands to extract milk from your breasts.
Most lactation consultants teach moms who breast feed how to manually express their milk whether they plan on pumping or not, just in case the need arises. After that, there are a variety of breast pumps to choose from. Your choice will depend on how you plan to use the pump and how often.

Manual, Battery or Electric

Here are some questions you should consider before you decide which type of breast pump to use: Will you use it to help increase the amount of milk you produce for your baby, or to have breast milk on hand should you need it? Will you use the pump once a week or several times a day? Will you be pumping one breast while the baby nurses at the other?
If you plan to pump your milk for a baby still in the hospital because it was born prematurely or if you plan to pump at least once a day or pump on one side while your baby nurses on your other breast (also called double pumping) then a high-end, self-cycling electric pump likely is your best option. For most any other use, manual expression of your breast milk with a hand pump or a battery-operated or small electric pump should meet your needs.
Hand pumps, or manual breast pumps, uses your hand and forearm strength to pump one breast at a time. They range in price from $15 to $50. Both manual expression and hand pumps take some practice and can be very tiring.
Battery-operated or electric pumps are easier to use, but also are more expensive. But if you're going back to work, an automatic pump may be well worth the cost. If you are only pumping occasionally, hand expression, a manual pump or a battery-operated pump may work for you. Fully automatic electric pumps are the best for women who need to pump over a long period of time.
Electric pumps are available in semi-automatic and self-cycling varieties as well as single and double models, so you can pump one breast or both breasts at the same time. Small electric pumps range from $30 to $150, while full-size pumps can cost $200 to $350. Hospital-grade pumps are the most expensive. They can cost as much as $1,000 or more. However, many hospitals, lactation consultants, and medical supply stores rent such breast pumps for $1 to $3 per day. Women who rent pumps also will have to buy the collection kit (plastic breast shields, tubing and collections bottles) for about $50.
Even though it's tempting to borrow a breast pump from a friend to save money, most are designed for a single user. Breast milk can be home to bacteria and viruses that can be passed along to your baby, no matter how hard you try to clean the machine. The best way to avoid potential trouble is to get your own breast pump.

Advantages & Disadvantages

Each type of breast pump has a plastic shield that covers the nipple. With some breast pumps, the milk passes through the shield and empties directly into a bottle. But with most breast pumps, the milk flows through a flexible plastic tube to the bottle or a plastic storage bag.
Some manual pumps use the foot and leg muscles to simulate suction. This type of pump is used for occasional use - once or twice a week - or to help increase milk production between times when the baby is nursing. While the manual pump that looks like a bicycle horn is still available, they can be difficult to clean and can hurt the breast. Instead, experts steer mothers who will be using manual pumps.
Like a manual pump, battery-operated pumps are useful for moms who want to pump once a day or less. The batteries help prevent muscle soreness in hands and arms, and are designed for single breast use.
However, for more than occasional use, small manual and battery pumps are less efficient than the larger electric models and mom has to work harder, longer to get less. Most of the smaller models don't mimic the baby's sucking cycle, so if they're used over a long period of time or frequently during the day, breast tenderness or soreness can result. In addition, the batteries must be replaced often and the motors of mini-electric pumps can burn out with frequent use.
Fully automatic electric pumps work the same way a baby at the breast would, starting with short, quick sucks then moving into a slower, deeper sucking pattern. These pumps help mothers produce more milk and maintain their production over time. Most also allow women to pump both breasts at the same time. This saves time and ensures both breasts are emptied fully. Most come with carrying cases with accessories included. Some offer AC adaptors for in-car use, and some come with a built-in backup battery.