Nutritional composition of breast milk produced by mothers of preterm infants.

Abstract

The development of intensive care neonatal units has resulted in the survival of an increasingly larger proportion of low birth weight infants, but many questions remain about the optimal method of feeding this group. It has been suggested that human milk may provide some protection against infection and necrotizing enterocolitis. 1 possibility is that the unique nutritional needs of the preterm infant are matched by the composition of breast milk produced by mothers delivering prematurely. Yet, it has been observed that rapidly growing low birth weight infants fed human milk in usual amounts may fail to put on weight and height at the rates achieved by formula-fed infants and are at risk of developing deficiencies of certain specific nutrients. These data have led to studies designed to evaluate the nutritional composition and adequacy of breast milk produced by mothers delivering before 37 weeks of gestation. Gross et al. determined the concentrations of protein, minerals, and electrolytes in milk obtained from 33 mothers giving birth between 28-36 weeks of pregnancy (preterm) and from 18 mothers delivering between 38-42 weeks of gestation (term). Energy values calculated on the basis of protein, lactose, and fat were similar in the 2 groups and remained constant throughout the 7-28-day postpartum period. Sodium and chloride levels were higher in preterm milk whereas the concentrations of potassium, calcium, phosphorous, and magnesium were similar in milk from both groups of mothers. In a similar study, Schanler and Oh also noted that the total nitrogen content in the milk of mothers delivering preterm was higher for the first 15 days than in a pool of donated milk expressed between 1-32 weeks after birth. The total nitrogen content was not related to alterations in volume of breast milk produced by the 2 groups of mothers. These recent reports confirm earlier observations of a greater concentration of nitrogen in the milk of mothers delivering preterm than in the milk of mothers delivering at term. The clinical significance of these differences is not established.