Background:Research about parity or breastfeeding experience and its relationship with milk production in humans is limited. The purpose of this study was to determine if any difference in milk volume occurred among mothers with and without breastfeeding experience who used either a single or double breast pumping regimen the first 5 weeks postpartum.Methods:A convenience sample of 39 mothers of nonnursing preterm infants participated from two tertiary care centers in the midwestern United States. The sequential single pumping group consisted of 20 mothers, 7 of whom had previous breastfeeding experience; the simultaneous double pumping group consisted of 19 mothers, 2 of whom had previous breastfeeding experience. Income and pumping group regimen were used as blocking variables, and average frequency of kangaroo care per week and average frequency of breast pumping per week were covariants in the repeated measures analysis of variance.Results:Mothers with previous breastfeeding experience had greater milk weights over time, but weights were not significantly different when compared with those mothers with no previous breastfeeding experience. Additional analysis with the covariants of pumping frequency and kangaroo care, and with the independent variables of group, breastfeeding experience, and income resulted in statistically significantly greater milk yield in the women with previous breastfeeding experience.Conclusions:The findings of the two repeated analyses indicated the complexity of the milk production response, and the importance of considerations of environmental as well as physiologic factors.