Biomechanics of Breastfeeding

Breastfeeding is strongly encouraged because breast milk provides both nutrients and immunities required for growth and development during the first months after transition from in utero to ex utero. It is less known that breast-fed infants exercise and prepare their oro-facial muscles for future tasks of speaking and chewing, and also have higher oxygen saturation than bottle-fed infants. The process of breastfeeding requires dynamic synchronization between oscillation of the infant's mandible, rhythmic motility of the tongue, and the breast milk ejection reflex that drives maternal milk towards the nipple outlet. It starts when the infant latches on to the breast and nipple so that the nipple, areola and underlying mammary tissue and lactiferous ducts are drawn into the infant’s mouth with the nipple tip extended as far as the hard-soft palate junction (HSPJ). Then, the infant moves its mandible up and down, compressing the areola and the underlying lactiferous ducts with its gums in a suckling process that extracts the milk into its mouth. In concomitant, spontaneous undulating motions of the infant tongue channel the milk posteriorly and trigger the swallowing reflex. During breastfeeding, suckling, swallowing and breathing are coordinated by the central nervous system in a way that allows for the infant's continuous feeding without breathing interruptions. We developed a dynamic analysis of ultrasound video clips acquired during breastfeeding in order to explore the tongue dynamic characteristics. The analysis of tongue motility during breastfeeding was compared between healthy infants and tie-tongue cases pre- and post-frenotomy, as well as between breast and bottle feeding. Then, we have developed a new three-dimensional biophysical model of the breast and lactiferous tubes that enabled mimicking the dynamic characteristics of the tongue and nipple observed in ultrasound imaging during breastfeeding, and thereby, exploration of the biomechanical aspects of breastfeeding. These computations have shown that latch-on to draw the nipple/areola into the infant mouth, as well as milk extraction during breastfeeding, require development of time varying sub-atmospheric pressures within the infant's oral cavity.