Thermal physiology of the lactating nipple influences the removal of human milk

The nipple has a critical role in successful breastfeeding. Nipple trauma or pain may negatively impact breastfeeding duration which has significant public health implications. The aim of this study was to examine changes in nipple temperature during breastfeeding and pumping within participants. Thirty lactating women participated in two pumping (electric breast pump) and one breastfeeding session. Nipple temperature of both breasts was monitored for two minutes before and after each session with the non-pumped/non-suckled nipple temperature recorded throughout each session. The mean increase in nipple temperature after milk removal by the infant was 1.0 +/- 1.6 degrees C (range -3.2-3.2) and after expression was 1.8 +/- 1.4 degrees C (range -0.9-6.1). Nipple temperature pre expression was significantly lower than post expression (Pre 32.6 +/- 1.6, Post 34.3 +/- 1.3, p < 0.001) with no difference between the two pumping sessions. For every 1 degrees C rise in temperature an additional 10 mL of milk was removed on average. The breastfed nipple temperature was significantly lower pre feed than post feed (Pre 32.4 +/- 1.6, Post 33.2 +/- 1.2 p = 0.01) with a significant but smaller change in nipple temperaturecompared to pumping (Breastfeed 1.0 +/- 1.6, Pumping 1.7 +/- 1.4, p = 0.03). Nipple temperature increases during pumping and breastfeeding suggesting the breasts have a similar physiological response to different stimuli. Further, the increased temperature potentially plays a role in effective milk removal.