Length of gestation and nutritional composition of human milk

A comparative analysis of the composition of milk produced during the first 14 days of lactation by mothers who deliver prematurely and those who deliver at term is described and these values are contrasted with the composition of donor milk specimens. Twenty-four-hour milk collections (days 3, 7, and 14 postpartum) were obtained from nine mothers delivered between 37 to 42 wk gestation (term) and from 14 mothers who delivered between 28 to 36 wk gestation (preterm). A single spot milk collection was obtained from nine mothers who were 6 to 10 months postpartum (donor). Term and preterm milk was compared on specific postpartum days using an analysis of covariance controlling for 24-h milk volume. The protein, carbohydrate, fat, and energy content varied in a similar fashion in term and preterm milk over the 14 postpartum days studied. Further, there was no significant difference between the two milk groups on any single postpartum day evaluated in terms of protein, carbohydrate, fat, or energy concentration. The milk volumes were significantly greater from the mothers delivered at term on days 7 and 14 (p < 0.01) and the protein content of both term and preterm milk was negatively correlated with milk volume (r = -0.6 or more on each day studied). The nutrient and energy composition of spot donor milk was highly variable and frequently quite different from either term or preterm 24-h milk collections. These data indicate that milk from mothers who deliver prematurely does not contain significantly different concentrations of nutrients or energy than milk from mothers delivered at term and suggest that the differences previously noted between the two groups may be related to 24-h milk volume.