BACKGROUND: Hypernatremic dehydration amongst exclusively breastfed neonates due to inadequate breastfeeding or underfeeding is a potentially devastating condition. We investigated the epidemiological and clinic features of hypernatremic dehydration. METHODS: We retrospectively reviewed the medical records of neonates that were less than 28 days of age, weighing > or =2000 g with gestational age of 36 weeks born between January 2002 and December 2005, who had meet the criteria of hypernatremic dehydration, including (1) exclusively breastfed; (2) loss of weight 12% or more from birth weight; and (3) serum sodium concentration of at least 150 mmol/L at presentation, that had been subsequently admitted to our institution. RESULTS: Totally nine cases were found during this four-year period, an incidence of 2.3 per 1000 live births. Involved infants’ age at presentation ranged from 3 days to 14 days (mean t Standard Deviation = 7 +/- [3.8]); five presented symptoms or signs within the first week of life. Study-involved infants featured a birth-weight loss ranging from 12% to 29% (mean +/- [SD] = 17.0 +/- [5.9]), and also hypernatremia (mean +/- [SD] = 153.5 +/- [3.2] mEq/L ). Sodium concentration of breast milk ranged from 15 mEq/L to 54 mEq/L (mean +/- [SD]= 36.0 +/- [14.32]). Subsequently, all were supplemented with breast milk or, alternatively, formula. None of the study-involved neonates suffered subsequent complications or a relapse of their condition. CONCLUSIONS: Neonatal hypernatremic dehydration due to inadequate breastfeeding or underfeeding would appear to be a rather common problem. In order to avoid serious morbidity and mortality, all breastfed infants should receive regular follow-up by health-care worker. Furthermore, we advocate that all mothers should be taught the skills of breastfeeding, and warning signs of breastfeeding failure and hypernatremia, accompanied with the monitoring of the weight of infants until growth commences, in order to reduce the likelihood of this condition arising, especially for first-time mothers. PMID: 18265538 [PubMed – indexed for MEDLINE