- A breast pump's main purpose is to efficiently and comfortably express milk. This is done by mimicking a baby's sucking action and stimulating the mother's milk-ejection reflex, also known as let-down, and thoroughly removing the milk. There are three types of breast pumps---manual pumps, battery-powered pumps and electric pumps---and each work differently to express milk, though all pumps have a few features in common. Every type of pump consists of a cone-shaped soft cup called a breast shield that fits over the mother's areolas and a pump that creates a vacuum to suction out milk that comes with a detachable container into which the milk is pumped. This container may be disposable or reusable. Each brand and type of pump works in different ways.
- Cycles are measured by one suck and release combination. To be efficient, a breast pump must simulate the sucking pattern of a baby, which is usually 40 to 60 cycles per minute. The pressure exerted on the nipple is measured in millimeters of mercury (mmHg). Babies usually exert 220 to 230 mmHg as they breastfeed and press down on the breast for less than a second. Breast pumps must have a vacuum pressure between 150 and 250 mmHg at the active sucking stage to be efficient without traumatizing the nipple.
- To use a manual breast pump, place the breast shield over the areola and squeeze the pump handle by hand. This will create a vacuum over the nipple. Air that will be pulled into the breast shield will apply and release suction as the handle is being pumped. This suction will stimulate the milk ejection reflex that will fill the container with fresh milk. Most manual breast pumps are single pumps---they consist of one breast shield that pumps only one breast at a time.
- Battery-powered and electric breast pumps work similar to manual ones but have either battery-powered motors or motors that plug into electric outlets and require no manual pumping. Electric pumps have a tube connected from the breast shield to the electric motor, which then plugs into an outlet. Automatic pumps run through the entire cycle of rapid sucking into slow "gulping" that is more like the natural sucking rhythm of a baby. Some pumps are fully adjustable. Double pumps can milk both breasts at the same time. Double-alternating pumps suction one breast and then the other when the suction is released. "Hands free" pumps can be worn inside bras or nursing tops.
