Introduction. The first year of life of a child, especially the first six months, is characterized by high rates of growth and development. The influence of the nature of feeding and nutrition is one of the factors determining the harmony of development, the formation of immunological reactivity and resistance to infectious diseases.The aim of the study was to assess the provision of micronutrients (phosphorus, calcium, magnesium) to nursing women and to determine their impact on the physical and neuropsychological development of children in the first six months of life.Materials and methods Babies aged 5 days to 6 months and their nursing mothers (n = 53) were prospectively followed up. Anamnestic data, objective examination, evaluation of physical and neuropsychological development, determination of calcium, phosphorus, and magnesium levels in the blood serum of nursing mothers, and determination of calcium, phosphorus, magnesium, and vitamin D in breast milk were studied.Results The indicators of physical development in most of the examined children were within ±2 sigma deviations (SD). In the evaluation of neuropsychological development, Group I children predominated. We found calcium, phosphorus, magnesium, vitamin D deficiency in breast milk samples (52.8 %; 5.6 %; 17.0 %; 7.7 %, respectively).Discussion Calcium deficiency in natal milk affects the formation of delayed neuropsychological development of the child, the development of subacute rickets, atopic dermatitis. When breast milk with high phosphorus content is fed, the child's body weight increases. However, the higher the level of magnesium in mother's milk, the lower the z-score on body weight / length and BMI / age in children. Low levels of magnesium in breast milk lead to the development of atopic dermatitis and greater susceptibility of the child to respiratory infections.Conclusion Inadequate provision of micronutrients to a nursing woman and the identified deviations in the child's health status dictate the need to introduce the monitoring of the actual nutrition of a nursing woman and the assessment of her nutritional status in order to prevent deviations in the health status of the child into outpatient visits of a district pediatrician.