Total body water ______ throughout gestation.

• A. Decreases
• B. Increases
• C. Remains constant
• D. Fluctuates

Answer: (A)

Total body water decreases as gestation progresses because the fetus gains more dry mass (fat, bone, protein) while the water content as a percentage of body weight declines. Early in gestation the fetus has a higher water proportion, and as tissues develop, the relative amount of water per kilogram drops. By term, TBW is about three-quarters of body weight, whereas earlier it is higher. So the best statement is that total body water decreases throughout gestation. The other options don’t fit because TBW does not steadily increase, remain constant, or fluctuate randomly with gestation.