How do fluid requirements change through life?

Infants:
Infants who are breast fed or formula milk fed in cold climates can obtain all their fluid requirements from breast or formula milk - 500 to 1000ml a day. In hot climates cooled boiled water is also needed because of increased sweating and moistening of expired air.

Children:
Children older than 2 years need 1000ml to 1500ml of fluid each day. Requirements increase from infancy because of a larger body size and increased physical activity. In hot climates, additional water is needed because of increased sweating.

Pregnancy:
Fluid requirements are greater during pregnancy becuase of increased flow of urine through the kidneys to help remove increased body wastes.
During pregnancy, alcohol should be avoided and caffeine-containing drinks such as coffee, cola, and tea need to be restricted. Alcohol crosses the placenta to the foetus. Caffeine is cleared from the body more slowly during preganancy, and may also cause the foetal heart rate to slow down.
Coffee also increases the secretion of stomach acid and decreases oesophageal sphincter pressure. These effects may contribute to nausea and vomitting.

Lactation:
A greatly increased amount of fluid is required during lactation, especially water. The usual amount of milk secreted is between 850ml to 1200ml each day. At least 4 to 6 cups of fluid above the usual intake is required.