High breast-milk sodium in cystic fibrosis [letter].

Increased sodium concentration in sweat is a characteristic of cystic fibrosis. However, 
we have read nothing on the sodium content of breast milk 
in this condition. A patient with sweat-test-proved cystic fibrosis with mild 
pulmonary disease had her first baby by normal delivery at term. 
Samples of breast milk were obtained on the sixth and seventh 
days post partum when the mother was not breast feeding. The 
two sodium concentrations were 132 and 280 mmol/l, concentrations much higher 
than in any other milk sample tested at this hospital in 
a large survey and higher than any we have seen in 
the literature. Milk of such high sodium content would be unsafe 
for a baby, and we suggest that, if mothers with cystic 
fibrosis were to breast feed, the sodium of the mild should 
be measured first. The breast, like so many other exocrine glands, 
seems to be affected by the secretory abnormalities of cystic fibrosis. 
