title: Asynchronous milk ejection in human lactating breast: case series.
abstract: BACKGROUND
  Milk production is under the influence of autocrine control such that the rate of milk synthesis decreases as the breast fills with milk. Effective elimination of milk from the alveoli via the milk ejection reflex will therefore result in increased milk synthesis. It has been assumed that milk ejection occurs in all alveoli simultaneously; however, animal studies have indicated that full alveoli eject milk sooner than less full alveoli, suggesting heterogeneous emptying of the mammary gland.
  
  
  OBJECTIVE
  The aim of this study was to determine whether milk ejection occurs asynchronously in the human lactating breast.
  
  
  METHODS
  Retrospective analysis of videos made of ultrasound monitoring of milk ducts during pumping. Six video clips (4 women) of ultrasound monitored milk ejections showed obvious differences in the timing of milk flow between different main milk ducts. Duct diameter was simultaneously measured every second in 2 different ducts that drained 2 separate lobes of the breast.
  
  
  RESULTS
  For 5 of 6 ultrasound duct monitoring sessions, both duct dilation and visualization of milk flow in the 2 separate main milk ducts differed by 2 to 8 seconds. For the remaining woman, milk was observed to eject from 1 part of the lobe, and when not removed, it flowed in a retrograde fashion into a different part of the lobe.
  
  
  CONCLUSIONS
  Asynchrony of milk ejection occurs in the human lactating breast, suggesting that the timing of myoepithelial cell response differs, resulting in heterogeneous emptying of the gland.
authors.affiliation: The University of Western Australia, Perth, Western Australia, Australia hazel.gardner@uwa.edu.au.
authors.forename: Hazel
authors.initials: H
authors.lastname: Gardner
authors.affiliation: The University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Jacqueline C
authors.initials: JC
authors.lastname: Kent
authors.affiliation: The University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Hartmann
authors.affiliation: The University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Donna T
authors.initials: DT
authors.lastname: Geddes
mesh_terms: D000328:Adult; D001942:Breast Feeding; D061186:Breast Milk Expression; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D042361:Mammary Glands, Human / Q000502:physiology*; D008893:Milk Ejection / Q000502:physiology*; D011247:Pregnancy; D012189:Retrospective Studies; D016217:Ultrasonography, Mammary; D014741:Video Recording
keywords: breastfeeding; lactation; let-down; milk ejection; oxytocin