Body water across life stages

The body-water fraction changes with age and also depends on body composition. It is often around 50–60% in adults and roughly 70–75% in infants; 80% is too high as a general figure for all children. In a fetus, the water fraction gradually falls as development progresses: classic data give about 87% at 20 weeks’ gestation (around month five), while about 94% is reported for an earlier stage, around 16 weeks. [1–4]