I think it does. The hen's body warms the egg and supplies humidity to help give the developing chick water. The egg releases the moisture into the humid air around it,so it gets lighter.
Egg shells are very porous, and water loss can be as much as several grams of water per day, depending on how many pores that an egg has and how the egg is handled. Water has to be lost from an egg in order to make room for water created via the metabolism of materials found in the egg. Egg washing will change the rate of water loss from the eggs and incubator conditions may need to be changed in order to compensate for this loss.
Humidity (% RH) must be adjusted to accommodate the needed moisture loss from the egg during incubation. Most ratite eggs will perform well when a moisture loss of 12-16% is achieved. This loss, as measured as a percentage of the set weight over 42 days incubation (see below), will be adjusted somewhat by the embryo as it creates water as the by-product of digestion of foods found in the egg. By weighing the egg at set time, and monitoring egg weight periodically through incubation, you can ensure the best humidity profile for optimal hatch. Water loss can be calculated several ways. One method is to calculate the percent water loss relative to the egg's set weight for a given period of time.