SUMMARY Plasma concentrations of motilin, gastrin, and enteroglucagon were measured in cord blood and during the first 24 days of life before feeding in 45 term and 63 preterm, healthy infants. Levels of these hormones rose steeply after birth, reaching concentrations that were much higher than those in fasting adults. These increases in hormone concentration were not present in a group of 10 preterm infants who had received only intravenous dextrose from birth because of hyaline membrane disease. Our findings suggest that early enteral feeding may trigger the postnatal increase in plasma concentrations of gut hormones and that this could play an important role in the physiological adaptations to extrauterine nutrition.At birth intravenous nutrition via the placenta ceases and the neonate must adapt to enteral feeding. By age 2 weeks the term neonate consumes a daily volume of milk which in an adult, on a proportionate body weight basis, would correspond to a fluid intake of 10-20 litres a day. Clearly the periodic administration of these large volumes of milk to neonates must necessitate adjustments in their gastrointestinal motility, and there is evidence to suggest that gastric emptying and upper intestinal transit time become more rapid during the first weeks of life both in term and preterm infants.1 In addition, animal studies demonstrate that early enteral feeding results in pronounced changes in the structure and growth of the alimentary tract, associated with enchancement of enzyme activities-for example in jejunal lactase and acid phosphatase: in contrast, these changes are not seen in unfed animals.2-4The triggering mechanism for the physiological and structural changes that occur after birth in the gastrointestinal tract of the human newborn is poorly understood, but it is possible that the secretion of gut hormones in response to enteral food plays a key role. We have studied 3 hormones (motilin, enteroglucagon, and gastrin) in the neonatal period.Motilin contains 22 amino-acids and is produced by endocrine cells of the upper small intestine.5 Since this peptide was isolated in 19716 there has been evidence to suggest that it is physiologically important in the control of gastrointestinal motility in adult man.7-8Gastrin, released from specific endocrine cells in the pyloric antrum and duodenum,9 and enteroglucagon, produced in highest concentrations in the ileum and colon, are of particular interest in the neonatal period because, in addition to their other functions, they may exert a trophic influence on the gastrointestinal tract (see below).In order to investigate the roles of motilin, enteroglucagon, and gastrin in the postnatal adaptation to enteral nutrition, we have measured plasma levels of these peptides in more than 100 term and preterm infants. [12][13][14][15][16][17][18][19][20][21][22][23][24]; preterm infants were sampled before the first feed at age 3-6 hours, or on day 2j(1-4), day 6 (5-7), day 13 (11-17)