In a prospective, no experimental and comparative analysis, the relationship between the mother's nutritional conditional and their macronutrient's concentrations was evaluated in 40 samples from mothers who had children 15 days to 6 months old, in a hospital setting at the Emergency room of the Pediatric Ward of Maracaibo's University Hospital in Maracaibo, Venezuela in one year period. Milk from two groups of 20 mothers each was analyzed: Group A (Experimental), mothers with undernourishment and Group B (Control), mothers with adequate nutritional status. Fat content was 3.8 +/- 0.32 g/dl and 5.5 +/- 1.08 g/dl respectively (p = 0.0001); proteins were 1.8 +/- 0.21 g/dl and 2.4 +/- 0.32 g/dl respectively (p = 0.0001), and carbohydrates were 6.06 +/- 0.43 g/dl and 5.7 +/- 0.45 g/dl respectively (p = 0.0136). In addition, caloric value was also different: 65.92 +/- 15. 16.68 kcal/l and 83.25 +/- 9.4 kcal/dl (p = 0.0002). The undernourished were in the range of group V Graffar Méndez-Castellano, confirming the relationship between undernutrition and poverty. It is concluded that the proteins, fat concentrations and the caloric value in the breast milk from undernourished mothers are of lower value than the nourished well mothers.