Technical Abstract: Mechanical characteristics of breast pumps have been shown to influence milk extraction and hormone release in laboratory settings. However, few studies evaluate impact of differences in pump design on long-term breastfeeding success. This study evaluated the impact of a novel pump design on milk extraction, milk fat content, maternal hormone response, maternal satisfaction, long-term milk production, and duration of breastfeeding following return to the workforce. Healthy women intending to return to work or school, and to breastfeed exclusively for less than 4 months were enrolled in late pregnancy (n = 62). Prolactin response to pumping (n = 30) and changes in 24-hour milk volume during a 2-week stimulation protocol (n = 59), were measured in women randomly assigned to a novel (Embrace, Playtex, Westport, CT) or standard (Pump In Style, Medela, Baar, Switzerland) electric breast pump. Milk extraction efficiency (n = 58) and maternal ranking of pump performance (n = 56) were measured using a crossover design. Mothers selected one pump to keep and were contacted (n = 55) at 6 months postpartum to determine breastfeeding behavior. Prolactin response was greater (p = 0.005) with the novel pump. Milk extraction efficiency was greater (p = 0.001) with the standard pump. Stimulation of 24-hour milk production did not differ between pumps. Women were equally likely to select the two pumps. Feeding behavior at 6 months was not related to pump choice. The test pumps stimulate the two arms of the homeostatic mechanism governing milk output (endocrine stimulation and degree of breast emptying) to different degrees yet have comparable impacts on lactation performance over time.