In Reply.—As reflected in our title, we believe the incidence of oral water intoxication is far greater than the medical literature suggests and that it increased rapidly in the 1980s. The patients described by Furth and Oski added to those of Medani1 increase to 58 the number of affected infants in one city, appearing to support our impression as to the increasing occurrence of this condition.
We speculated that the clustering at age 4 months occurs because that is when the infants "outgrow" the allotment from the Women, Infants, and Children program (one can of formula per infant per day from birth to age 365 days). Furth and Oski found fewer mothers who said that they had exhausted their supply of formula, leading these authors to conclude that multiple causes of this problem exist. All three studies are retrospective reviews, so the maternal motivation for offering water remains uncertain.
KEATING JP, DODGE PR. Hyponatremia and Water Intoxication-Reply. Am J Dis Child. 1993;147(9):933. doi:10.1001/archpedi.1993.02160330022007