Background: Expressing human milk using commercially available pumps has increased. Most women use mechanical means to transfer their milk at some point during lactation. Yet, there is very little quantification of any breast tissue changes that occur when using mechanical devices to facilitate milk transfer. Objective: Women comfortable with breastfeeding were recruited to participate in a study to measure physical changes of the breast with a variety of human milk transfer modalities under close observation. Materials and Methods: Direct breastfeeding with their infant, hand expression, and mechanical milk transfer using two commonly available breast pumps were utilized over four milk transfer sessions with each participant. Each participant directly breastfed on the first milk transfer session and the remaining modalities were randomized. Measurements were taken before and after each modality using digital calipers. Participants completed a modified pain scale after each observation. Measurements taken after breastfeeding were used as the control for data interpretation for each participant. After a 20-minute rest period, breast tissue was again examined, and tissue appearance was recorded. Within-subject modality differences were calculated, and paired analysis mean difference and standard error of the mean are presented. Results: Fifty eligible women were approached with 92% participating. The "before" measurements were not significant for all the modalities. The "after" measurements were significantly different at p < 0.003 for breast pumps but not for breastfeeding or hand expressing. Many participants indicated pain with pumping. Conclusion: Mechanical pump use correlated with significantly increased length and diameter of the nipple compared with the post-breastfeeding and hand expressing dimensions. Pump use correlated with significant pain scores and resulted in localized inflammatory changes. Understanding how pumps affect breast tissue is helpful in improving experiences with breast pumps and may improve breastfeeding outcomes. Additional research is needed to better understand ramifications of long-term use of breast pumps.
Keywords: breast pump; breast tissue; lactation; milk expressing; milk transfer.