Children: What is the weight loss of babies?

The children at birth, weigh, on average, ranging between 2.8 and 3.8 kg, a difference between boys and girls, in the sense that the latter tend to be tiny. The baby, however, in the first days after birth, "slim," he observes, that a weight loss of about 10% of the total weight. Why? This is an absolutely normal, which should not in any way concern the new mother and that doctors call "physiological".