Background Hypernatremic dehydration is a potentially lethal condition that can cause major neurological complications in neonates. The increased number of reports in breast-fed neonates reinforces the need for a good surveillance and evaluation of breast-feeding techniques.

Clinical case Male infant, first-born to a Graffard class III family (vaginal delivery, GA- 35 weeks, BW-2370 g), discharged at 48 h, maintaining exclusive breast-feeding.

On day 5, metabolic screening was made at the primary healthcare center (PHCC). The first appointment was scheduled to 1.5 months and weight was not assessed.

On day 15, weight was assessed by the parents, as the PHCC was closed: he weighed 2050 g fully clothed, which was interpreted as the “normal weight loss of the first days”.

On day 21, because of additional weight loss and lethargy, he was brought to the hospital. Suction was referred to be vigorous and feeding intervals>4 h. Observation revealed a lethargic, malnourished baby, with a weight loss of 40% his BW. Laboratory tests: Hb-17.9 g/dl, WBC- 20800(40%N), Na+-196 mEq/L, urea- 271 mg/dl, creatinin-1.7 mg/dl, pH-7.10, HCO3-14.6 mEq/L, glucose-53 mg/dl, CRP<0.3 mg/dl.

Slow IV correction was started, but still he had seizures at day 3 of admission.

Cerebral ultrasound was normal. He was discharged 28 days after admission, clinically well.

Discussion Breast-feeding failure can lead to hypernatremic dehydration in neonates. Precocious weight assessment, clinical and breast-feeding evaluation are recommended in order to prevent and recognize these situations as early as possible.

The failure of all health surveillance mechanisms associated to a very low maternal knowledge on breast-feeding, could have lead to the death of a healthy newborn.