At birth, which of the following statements is true?

At birth, a significant transition occurs in the circulatory and respiratory systems, marking the infant's adaptation to life outside the womb. The statement that there is a shift in gas exchange from the placenta to the lungs is accurate. Before birth, the placenta acts as the primary site for gas exchange, where oxygen and nutrients are provided to the fetus while carbon dioxide and waste products are expelled.

Upon delivery, the infant's lungs expand for the first time as they take in air. This dramatically changes the dynamics of blood flow and gas exchange. The lungs become the main organ for oxygen uptake and carbon dioxide elimination. This transition is critical for survival outside of the womb and involves various physiological changes, including increased blood flow to the lungs, decreased pulmonary vascular resistance, and increased systemic vascular resistance as the umbilical cord is clamped and the placental circulation is disconnected.

In summary, the correct choice emphasizes the crucial shift in gas exchange from the placenta to the lungs at birth, which is fundamental for the newborn's respiratory function and overall adaptation to the environment.