A small body of low-quality trials, alongside limited observational studies and case studies support the recommendation for moderate exercise intensities in breastfeeding women. [1-4] There is no conclusive evidence to suggest that exercising at moderate intensities affects infant breast milk intake or growth ; alters the immunologic or mineral components of breast milk, [2, 5-7]; nor does there appear to be any positive association with increased lactic acid levels in breast milk following moderate-intensity exercise.  Two case studies have been published documenting potential risks of exercise participation whilst breastfeeding. The first described a case of exercise-associated hyponatraemia in a young woman actively breastfeeding two children having acutely increased her exercise frequency and intensity, whilst seemingly being advised to over-hydrate , and another describing a rare case of lactation ketoacidosis in a young woman who had recently reduced her carbohydrate intake and increased her exercise frequency .
Quality of Evidence
Strength of Recommendation
Moderate-intensity exercise can be recommended for the majority of breastfeeding women without concern about infant milk intake or the effect of exercise on breast milk composition. Care should be taken in the case of energy restriction through diet and acute increases in exercise frequency and/or intensity.
- Lovelady, C. A., Fuller, C. J., Geigerman, C. M., Hunter, C. P., & Kinsella, T. C. (2004). Immune status of physically active women during lactation. Medicine and science in sports and exercise, 36(6), 1001-1007.
- Lovelady, C. A., Hunter, C. P., & Geigerman, C. (2003). Effect of exercise on immunologic factors in breast milk. PEDIATRICS-SPRINGFIELD-, 111(3), 420-420.
- Su, D., Zhao, Y., Binns, C., Scott, J., & Oddy, W. (2007). Breast-feeding mothers can exercise: results of a cohort study. Public health nutrition, 10(10), 1089-1093.
- McCrory, M. A. (2000). Aerobic exercise during lactation: safe, healthful, and compatible. Journal of Human Lactation, 16(2), 95-98.
- Gregory, R. L., Wallace, J. P., Gfell, L. E., Marks, J., & King, B. A. (1997). Effect of exercise on milk immunoglobulin A. Medicine and science in sports and exercise, 29(12), 1596-1601.
6.Lovelady, C. A., Williams, J. P., Garner, K. E., Moreno, K. L., Taylor, M. L., & Leklem, J. E. (2001). Effect of energy restriction and exercise on vitamin B-6 status of women during lactation. Medicine and science in sports and exercise, 33(4), 512-518.
7.Fly, A. D., Uhlin, K. L., & Wallace, J. P. (1998). Major mineral concentrations in human milk do not change after maximal exercise testing. The American journal of clinical nutrition, 68(2), 345-349.
8.Quinn, T. J., & Carey, G. B. (1999). Does exercise intensity or diet influence lactic acid accumulation in breast milk?. Medicine and science in sports and exercise, 31(1), 105-110.
9.Bailowitz, Z., Raymond Grams, I. I., Teeple, D., & Hew-Butler, T. (2017). Exercise-associated hyponatremia in a lactating female. Clinical Journal of Sport Medicine, 27(4), e55-e57.
10.Al Alawi, A. M., & Falhammar, H. (2018). Lactation ketoacidosis: case presentation and literature review. BMJ case reports, 2018, bcr-2017.