Development of bowel habit in preterm infants.

The bowel habits in 844 preterm infants were observed during the first 56 days after birth. Delay in the passage of meconium beyond the second day occurred in 32%, and there was an inverse relation between gestational age and the day of first bowel action. Thereafter the increase in frequency of stools passed each day was related directly to the volume of milk ingested. Unfed infants had a modal defecation rate of one stool each day. For each 50 ml/kg increase in the volume of milk ingested the infants showed a further increase of one stool passed each day. Infants fed with human milk passed a greater number and softer stools than those who received cows' milk formula. In the absence of milk feeds an intrinsic pattern of large bowel motor activity, present as early as 25 weeks' gestation, ensures a defecation rate of one stool each day. The effect of enteral nutrition on this inherent motility is governed by the volume and composition of milk feeds, independently of gestational age.