For curious moms like us who want to understand more about the science :)

Measurement of tongue-artificial nipple contact force in infants with sucking difficulties.

Subjects were 20 healthy infants (Group A) and 5 infants who had difficulty sucking (Group B). The latter could not breastfeed well
and were fed from bottles or tubes. Informed consent was provided by the parents or guardians. The measured
maximum force at the tip of the nipple was 1.4 ± 0.4 N and 1.2 ± 0.3 N (mean ± SD) in Groups A and B, respectively. At the base of the nipple, the maximum force recorded was 0.8 ± 0.5 N and 0.3 ± 0.3 N (mean ± SD), respectively, showing a statistically significant difference (p<0.05). The sucking period was 0.6 ± 0.1 s (mean ± SD) in both groups. The difference in time necessary to reach the maximum forces between the sensors at the tip and base was 39.7 ± 28.8 ms (mean ± SD) and 37.2 ± 75.9 ms in Groups A and B, respectively.
Conf Proc IEEE Eng Med Biol Soc. 2013;2013:616-9. doi: 10.1109/EMBC.2013.6609575.

Biomechanics of milk extraction during breast-feeding

How do infants extract milk during breast-feeding? We have resolved a century-long scientific controversy, whether it is sucking of the milk by subatmospheric pressure or mouthing of the nipple– areola complex to induce a peristaltic-like extraction mechanism. Breast-feeding is a dynamic process, which requires coupling between periodic motions of the infant’s jaws, undulation of the tongue, and the breast milk ejection reflex. The physical mechanisms executed by the infant have been intriguing topics. We used an objective and dynamic analysis of ultrasound (US) movie clips acquired during breast-feeding to explore the tongue dynamic characteristics. Then, we developed a new 3D biophysical model of the breast and lactiferous tubes that enables the mimicking of dynamic characteristics observed in US imaging during breastfeeding, and thereby, exploration of the biomechanical aspects of breast-feeding. We have shown, for the first time to our knowledge, that latch-on to draw the nipple–areola complex into the infant mouth, as well as milk extraction during breast-feeding, require development of time-varying subatmospheric pressures within the infant’s oral cavity. Analysis of the US movies clearly demonstrated that tongue motility during breast-feeding was fairly periodic. The anterior tongue, which is wedged between the nipple–areola complex and the lower lips, moves as a rigid body with the cycling motion of the mandible, while the posterior section of the tongue undulates in a pattern similar to a propagating peristaltic wave, which is essential for swallowing. 5230–5235 | PNAS | April 8, 2014 | vol. 111 | no. 14

Maternal and Breast Pump Factors Associated with Breast Pump Problems and Injuries

The sample included 1844 mothers. About 62% and 15% of mothers reported pump-related problems and injuries, respectively. The most commonly reported problem was that the pump did not extract enough milk and the most commonly reported injury was sore nipples. Using a battery-operated pump and intending to breastfeed less than 12 months were associated with higher risks of pump-related problems and injury. Learning from a friend to use the pump was associated with lower risk of pump-related problems, and using a manual pump and renting a pump were associated with a higher risk of problems. J Hum Lact. 2014 Feb;30(1):62-72

The Mechanics of Breast Pumping: Compression Stimuli Increased Milk Ejection.

It was found that volume milk ejection together with vacuum and compression stimuli was 10-46% more than expressing only with vacuum stimuli. Average values were 40.5% ± 5% for expression only with vacuum stimuli and 59.5% ± 5% for expression with vacuum and compression stimuli. Breastfeed Med. 2016 Sep;11:370-5.

Feedback Control of Milk Secretion from Milk

This protein, termed FIL (feedback inhibitor of lactation), acts by reversible blockade of constitutive secretion in the mammary epithelial cell. As the inhibitor is synthesized in the same epithelial cells, feedback inhibition is, therefore, an autocrine mechanism. FIL's unusual mechanism of action also influences other aspects of mammary function. Acute disruption of mammary membrane trafficking is associated with downregulation of prolactin receptors and followed by a decrease in epithelial cell differentiation. Thus, in addition to acutely-regulating milk secretion, FIL may induce the adaptation in mammary cell differentiation which acts in vivo to sustain the secretory response to a sustained change in milk removal. In the long term, matching of milk output to demand is achieved by a change in mammary cell number. This developmental response is also local in nature. J Mammary Gland Biol Neoplasia. 1996 Jul;1(3):307-15.