What happens to the systemic vascular resistance (SVR) in a newborn after the umbilical cord is clamped?

After the umbilical cord is clamped, systemic vascular resistance (SVR) increases in the newborn. This physiological change occurs because, with the clamping of the cord, the newborn transitions from a placental circulation, which has low vascular resistance, to a systemic circulation that requires the lungs to oxygenate blood. Before the cord is clamped, the fetus receives oxygen and nutrients through the placenta, which results in a low-resistance pathway.

Upon clamping the cord, blood flow is redirected, and the newborn's own circulatory system begins to function independently. The pulmonary circulation also starts to develop as the baby begins to breathe air, contributing to an increase in SVR. This is vital for establishing the newborn’s independent cardiovascular system and ensuring efficient circulation. The increased SVR is essential to maintain adequate blood pressure and perfusion to vital organs.

Understanding this change is crucial for neonatal care, as it helps in recognizing the newborn's transition from fetal to extrauterine life and the necessary adaptations that occur in the cardiovascular system.