Neonatal Nurse Practitioner Practice Exam

Which process occurs in response to increased pulmonary vascular resistance (PVR) in fetuses?

1. Increase in lung perfusion

2. Constricted blood vessels

3. Decrease in heart rate

4. Enhancement of fetal movement

The correct answer is: Constricted blood vessels

When there is an increase in pulmonary vascular resistance (PVR) in fetuses, the body responds by constricting blood vessels. This physiological response is a crucial adaptation, as it helps to redirect blood flow away from the lungs, which are not yet functioning in gas exchange until birth. In a fetal environment, the lungs are filled with amniotic fluid, and since oxygenated blood comes from the placenta, there is no need for the fetus to utilize the lungs at that stage. Constricting blood vessels in the pulmonary circulation limits the amount of blood flowing to the lungs, which would otherwise be wasted since the fetus receives oxygen through the placenta. This reduced perfusion to the lungs is a protective mechanism that ensures that the blood is routed to areas that are vital for growth and development. Additionally, increased PVR typically occurs in certain conditions, such as when there is a need for the fetus to transition its circulatory system in anticipation of birth, where the lungs will become functional. It's essential for fetal circulation to remain efficient, and constricted blood vessels serve this purpose effectively. In contrast, processes like an increase in lung perfusion or enhancements in fetal movement would not be expected in response to increased PVR, and a decrease in heart