Gangliosides, found in blood, tissues and in human breast milk, are sialic acid-containing glycosphingolipids with implicated bioactivities in neural and brain development, maturation of the gastrointestinal tract, and the immune system. In a cross-sectional study, high performance liquid chromatography-mass spectrometry was used to measure the average total ganglioside concentrations in Malaysian mothers' colostrum and transitional milk; results were 26.8 and 18.9 mg L −1 , respectively. In mature milk, the average ganglioside concentrations at 2, 6, and 12 months lactation were 14.8, 25.3, and 16.6 mg L −1 , respectively. Considering the data from the typical exclusive breast feeding period (2 and 6 months) and adjusting for outliers, the trimmed mean was 18.5 mg L −1 . The average total ganglioside concentrations in maternal serum increased from 14.7 mg L −1 during the second trimester to 19.6 mg L −1 during the third trimester. However, in 45% of the mothers total serum ganglioside decreased in the third trimester. [ABSTRACT FROM AUTHOR]