Prevention of hypernatraemic dehydration in breastfed newborn infants by daily weighing

Hypernatraemic dehydration, which predominantly appears in breastfed neonates, can cause serious complications, such as convulsions, permanent brain damage and death, if recognised late. Weight loss ≥10% of birth weight could be an early indicator for this condition. In this prospective cohort study from October 2003 to June 2005 in the postnatal ward of the University Hospital Zurich, Switzerland, all term newborns with birth weight ≥2,500 g were weighed daily until discharge. When the weight loss was ≥10% of birth weight, serum sodium was measured from a heel prick. Infants with moderate hypernatraemia (serum sodium = 146–149 mmol/l) were fed supplementary formula milk or maltodextrose 10%. Infants with severe hypernatraemia (serum sodium ≥150 mmol/l) were admitted to the neonatal unit and treated in the same way, with or without intravenous fluids, depending on the severity of the clinical signs of dehydration. A total of 2,788 breastfed healthy term newborns were enrolled. Sixty-seven (2.4%) newborns had a weight loss ≥10% of birth weight; 24 (36%) of these had moderate and 18 (27%) severe hypernatraemia. Infants born by caesarean section had a 3.4 times higher risk for hypernatraemia than those born vaginally. All newborns regained weight 24 h after additional fluids. Conclusion: In our study, one out of 66 healthy exclusively breastfed term neonates developed hypernatraemic dehydration. Daily weight monitoring and supplemental fluids in the presence of weight loss ≥10% of birth weight allows early detection and intervention, thereby preventing the severe sequellae of hypernatraemic dehydration.