Growth factor concentrations and growth-promoting activity in human milk following premature birth.

We have measured growth factor concentrations in human milk from mothers of term and premature infants to identify any adaptive responses to premature delivery. Measurements included concentrations of epidermal growth factor and insulin and the growth-promoting activity of milk in vitro, estimated by the stimulation of rats of protein accumulation in cultured human fibroblasts. Compared with women delivering at full-term, mothers of premature infants produced milk containing higher concentrations of epidermal growth factor and increased growth-promoting activity in vitro, changes which were probably maintained throughout lactation. The anabolic effect of human milk in cultured human fibroblasts could be attributed partially but not entirely to epidermal growth factor, suggesting that the concentrations of additional growth factors were also increased following premature delivery. Insulin did not contribute to the extra growth-promoting activity; premature delivery depressed the insulin concentration significantly on the first two days of lactation and, thereafter, milk from mothers of term or premature infants contained similar amounts of insulin. Growth factor concentrations were also measured in cow's milk-based formulae. These formulae contained low concentrations of epidermal growth factor and insulin and reduced growth-promoting activity compared with human milk. Changes in milk growth factor concentrations may occur as a compensatory mechanism to accelerate growth and development in pre-term infants, and if so, it follows that premature infants could benefit more from their own mother's milk than from pooled human milk or from cow's milk-based formulae.