Neonatal Nurse Practitioner Practice Exam

What is a common cause of postnatal weight loss in the first week of life?

1. A contraction of extracellular fluid

2. A contraction of intracellular fluid

3. Decrease in intravascular volume

4. Inadequate feeding

The correct answer is: A contraction of extracellular fluid

The common cause of postnatal weight loss in the first week of life is a contraction of extracellular fluid. In newborns, especially those who are breastfed, it is typical for them to lose weight during the first few days after birth. This early weight loss is primarily due to the loss of excess extracellular fluid, which accounts for a significant portion of their body water. In the neonatal period, the body undergoes several adjustments as it prepares for feeding and adapting to life outside the womb. As infants transition from a fluid-filled environment in the uterus to a dry world, they begin to excrete excess fluid in urine and sweat, leading to a decrease in extracellular fluid. This fluid balance is primarily regulated through changes in feeding patterns and hydration status. This weight loss is generally considered normal, as long as it does not exceed the typical threshold (around 7-10% of body weight) and the infant is feeding adequately after the initial days. Other causes, such as a decrease in intravascular volume or inadequate feeding, while potentially relevant in some clinical contexts, do not commonly explain the typical weight loss seen during this immediate postnatal period. Thus, recognizing that contraction of extracellular fluid is a normal physiological process is key to understanding