Regarding body fluid compartments in a full-term neonate compared with a lean adult male, which statement is CORRECT?

• A Total body water is a smaller fraction of body weight, and ECF predominates over ICF
• B Total body water is a larger fraction of body weight, and ECF predominates over ICF ✓
• C Total body water is a larger fraction of body weight, and ICF predominates over ECF
• D Total body water is a similar fraction of body weight, and ECF equals ICF

Explanation

At birth total body water constitutes about 75 to 80 percent of body weight, falling toward 60 percent in adulthood as fat accumulates. In the fetus and neonate the extracellular compartment exceeds the intracellular compartment, a relationship that reverses during infancy as cells accumulate mass and ECF contracts. This high ECF fraction explains the neonate's larger insensible losses, greater vulnerability to dehydration, and the different fluid prescription calculations used in pediatric practice. Adult proportions of two thirds intracellular water are reached only later in infancy.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.