On the basis of data collected in a survey of the practices in maternity wards in Poland, we analysed newborn body weight differences between two groups of hospitals: one with the highest percentage of exclusive breastfeeding and other supportive practices, the other with the lowest. The aim of the study was to investigate whether hospital procedures can influence the newborn weight profile in the first days after birth. Healthy infants--normal birth, birthweight > or = 2500 g, discharged within 2-7 days, no missing data--were chosen for the analyses. The difference between discharge and birthweight, percentage of birthweight loss or gain on the day of discharge and percentage of the infants who at least regain birthweight on the day of discharge were compared between the two groups of hospitals. All analyses indicated the positive influence of exclusive breastfeeding and practices supporting it on infant body weight profile while in hospital.