Researchers at the Ohio State University Wexner Medical Center worked with academics from the University of California, San Diego, Arkansas Children’s Nutrition Center and the Joslin Diabetes Center to highlight how moderate exercise in mothers could benefit children in the long run through breast milk. They found that maternal exercise causes adaptations in breast milk which included an increase in oligosaccharide 3'Sialyllactose (3'SL.)
It sounds complex but 3’SL is responsible for the development of key immunoprotective effects [carbosynth.com] in newborns. It aids the development of the immune system and gut microbiota and suppresses adhesion and infectivity of bacteria and viruses, such as influenza viruses.
[...] “What we have shown in mice is that the offspring, as they age, do not become as obese and are less likely to develop type two diabetes, and female offspring are protected from heart failure as they age. More studies need to be done to determine how this will affect human infants,” says Stanford, “I think this study highlights the importance of maternal exercise. Even moderately increasing your activity during pregnancy could have pretty dramatic effects on your child's health.”
Johan E. Harris, Kelsey M. Pinckard, Katherine R. Wright, et al. Exercise-induced 3′-sialyllactose in breast milk is a critical mediator to improve metabolic health and cardiac function in mouse offspring, Nature Metabolism (DOI: 10.1038/s42255-020-0223-8 [doi.org])