Comparison of breast- and formula-fed normal newborns in time to first stool and urine.

BACKGROUND: Although the time to an infant's first stool is used as a marker for a normal GI tract, there have been no studies to date which have evaluated the contribution of the first 24 hours' feeding type to time to first meconium stool, directly comparing breast feeding vs formula feeding. OBJECTIVE: To compare breast- and formula-fed healthy infants > or =34 weeks gestation in time to first stool and urine. STUDY DESIGN: A chart review of 1000 consecutive infants > or =34 weeks of gestational age admitted to the normal newborn nursery of Children's Hospital of Buffalo from June to October 2000. Infants (n=979) were grouped based on feeding type in the first 24 hours: breast-fed (n=211), formula-fed (n=540), and mixed feeding (n=228); n=21 excluded for Neonatal Intensive Care Unit admission. We initially compared the time to first stool and urine between the breast- and formula-fed groups and then examined multiple maternal and infant demographic and clinical factors for their effect on time to first stool using univariate and multivariate analyses. RESULTS: Breast-fed infants were fed earlier and more frequently than formula-fed but there was no significant difference in time to first stool (7.6 vs 7.9 hours). Breast-fed infants were earlier in time to first urine (p=0.03) (7.3 vs 8.5 hours). In multiple regression analysis, gestational age was the only significant (p=0.000) factor in predicting time to first stool. CONCLUSION: Type of feeding did not predict time to first stool but gestational age was important even in this near-term and term population of infants > or =34 weeks gestation.