Why do term infants have a positive sodium balance?

Term infants exhibit a positive sodium balance primarily because they can efficiently reabsorb sodium. At birth, the renal system is sufficiently developed in term infants to handle sodium regulation effectively. This capability allows their bodies to maintain appropriate sodium levels, which is crucial for various physiological processes, including fluid balance, electrolyte homeostasis, and cellular functions.

The efficiency of sodium reabsorption is facilitated by well-developed renal tubular structures, enabling the infant to conserve sodium from their diet, which consists primarily of breast milk or formula that contains appropriate amounts of sodium. As a result, their bodies retain sodium, leading to a positive sodium balance, which is essential for optimal growth and development in the early days of life.

Understanding the mechanisms of sodium balance in term infants highlights their physiological development and the importance of adequate nutritional support, ensuring that they receive sufficient sodium based on their metabolic needs.