Breast milk production works on the principal of supply and demand. The more breast milk your nursing baby consumes, the more your body will manufacture.  

There are many situations in which you may need to pump milk. Some are short term - for example, occasional separations, taking a medication incompatible with breastfeeding, breast engorgement, severe nipple soreness, or increasing milk supply. Some are long term - a premature hospitalized infant, or regular separations such as when you may return to work or school.  In addition, mothers today often have to combine breastfeeding with other activities and responsibilities. You may also wish to involve other family members in feeding the baby.

There are several different types of breast pumps to choose from. Whichever pump you decide to use, it's a good idea to try it out well before you return to work or leave your baby with a caregiver.

There are many styles and models of breast pumps, but they often fall into three general categories: manual, battery-operated or electric.

Manual breast pumps require you to pump a piston or squeeze a handle to create the suction to empty your breast. They are lightweight, easy to take with you, and work quietly so you can express milk discreetly anywhere, anytime. These pumps empty only one breast at a time and may require two hands to operate, although a few are designed for one-handed use. While some moms can get the hang of effective manual pumping, others find these pumps very slow and tiring on their hands. However, newer models have been developed that only need occasional compressions on the handle after achieving let-down. This type of pump is best for women who only have to pump occasionally.

Battery-operated pumps are another option for occasional pumping. Handheld battery-operated breast pumps use batteries for creating suction. These pumps are portable but generally take a little longer to express milk. A drawback of battery-operated pumps is that the battery needs to be changed very frequently, which can be costly.

Electric breast pumps are made with either single or double pumping capabilities. Double electronic pumps are the best choice if you are a full-time working mother or are pumping and bottle feeding milk instead of breastfeeding. Double pumps allow for milk to be expressed from both breasts at once, resulting in a much faster, more convenient and efficient pumping session. Some newer models are providing unparalleled convenience and comfort. They are designed to imitate a baby's own suckling pattern and have features that learn and adapt to the mother. Most new models also come with all you need when pumping on-the-go, allowing you to easily pump, store and feed milk. Single electronic breast pumps are a less-expensive alternative to a double and are well suited if you work part-time or are at home. While they have most of the same features as a double pump, the single tends to be less effective at keeping up milk supply for women who pump one or more times per day and single pumping takes twice as long as double pumping.

Newer models of both the single and double pumps also can serve as a manual or battery-operated pump too.

If you'll be away from the baby only occasionally, a manual pump may be all you need. These pumps are small and inexpensive. If you're returning to work full-time or you're planning to be away from your baby for more than a few hours a day, you may want to invest in an electric pump. Electric pumps stimulate the breasts more effectively than hand pumps. This helps empty your breasts and protect your milk supply.

Electric breast pumps are faster than manual pumps. If you'll be pumping at work or in other time-crunched situations, you may want to invest in a model that allows you to pump both breasts at once. Double breast pumps help stimulate milk production while cutting pumping time in half. While pumping times will vary, most women find that single pumping takes 20-30 minutes and double pumping takes 10-15 minutes.

If the breast pump is difficult to assemble, take apart or clean, it's bound to be frustrating - which may reduce your enthusiasm for pumping. Make sure you can remove any parts of the pump that come in contact with your skin or milk for cleaning after use and ensure the pump has protection against back flow of milk into the tubing or motor. All breast pumps are accompanied with an owners manual and do not hesitate to call the customer service number provided if you have questions.

What's comfortable for one woman may be uncomfortable for another. Choose a pump that allows you to control the degree of suction. Some manual models allow you to adjust the position of the pump handle.

If you'll be toting the pump to work every day or traveling with the pump, look for a lighter-weight model. Some breast pumps come in a carrying case with an insulated section for storing expressed milk.

Some electric models are quieter than others. If it's important to be discreet, make sure the pump's noise level is acceptable. Visit a baby fair or ask for an in-store demonstration.

An electric pump needs to be plugged in. If an outlet isn't accessible, you'll need a rechargeable battery pack. Some models offer adapters that run on a car's cigarette lighter.

When evaluating the cost of a pump, remember that the cost of infant formula will far exceed the amount of money you will spend on a breast pump. You can buy breast pumps from medical supply stores and most drug and baby stores. Manual models cost less than $50. Electric pumps that include a carrying case and insulated section for storing milk may cost more than $300. Some hospitals rent hospital-grade breast pumps, although the equipment that attaches your breast to the pump must be purchased. Because there is a risk of contamination, borrowing a breast pump or buying a used pump isn't recommended. Additionally, a borrowed pump that has been used extensively may no longer have adequate suction, which will ultimately decrease your milk supply. Find out if your health insurance plan covers the cost of buying or renting a breast pump.

Ask for help. A midwife or lactation consultant can help you make the best choice - and offer support as you start to use your breast pump or if you run into trouble. If you haven't worked with a midwife previously, visit myMidwife.org for more information.  To learn about lactation consultants, visit the International Lactation Consultant Association.