Final answer:
It is normal for a newborn to lose up to 10% of their birth weight during the first week of life, although an unexpected weight loss after this period may be concerning and require further assessment. Infant growth is rapid in the early months, with expected weight doubling by six months and tripling by one year of age.
Step-by-step explanation:
It is considered normal for a newborn to lose up to 10% of their birth weight during the first week of life. This initial decrease in weight right after birth can be attributed to the resorption and urination of the fluid that initially fills the lungs, as well as a delay in feeding becoming well-established, which is also a normal occurrence. After this first week, a healthy neonate should start to gain weight, with an expected increase of up to 20 g (0.7 oz) per day.
Infant growth is particularly rapid during the first few months following birth. A normal infant generally doubles its birth weight by six months and triples it by 12 months. However, if an infant were to lose weight unexpectedly after the initial adaptation period, especially between the third and fourth weeks, this could be of concern and may warrant further investigation to ensure the baby's health and nutrition.